WIP

81 files changed, 24572 insertions, 0 deletions

diff --git a/libs/bs4/__init__.py b/libs/bs4/__init__.py
new file mode 100644
index 000000000..95ca229c1
--- /dev/null
+++ b/libs/bs4/__init__.py
@@ -0,0 +1,616 @@
+"""Beautiful Soup
+Elixir and Tonic
+"The Screen-Scraper's Friend"
+http://www.crummy.com/software/BeautifulSoup/
+
+Beautiful Soup uses a pluggable XML or HTML parser to parse a
+(possibly invalid) document into a tree representation. Beautiful Soup
+provides methods and Pythonic idioms that make it easy to navigate,
+search, and modify the parse tree.
+
+Beautiful Soup works with Python 2.7 and up. It works better if lxml
+and/or html5lib is installed.
+
+For more than you ever wanted to know about Beautiful Soup, see the
+documentation:
+http://www.crummy.com/software/BeautifulSoup/bs4/doc/
+
+"""
+
+__author__ = "Leonard Richardson ([email protected])"
+__version__ = "4.8.0"
+__copyright__ = "Copyright (c) 2004-2019 Leonard Richardson"
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+__all__ = ['BeautifulSoup']
+
+import os
+import re
+import sys
+import traceback
+import warnings
+
+from .builder import builder_registry, ParserRejectedMarkup
+from .dammit import UnicodeDammit
+from .element import (
+    CData,
+    Comment,
+    DEFAULT_OUTPUT_ENCODING,
+    Declaration,
+    Doctype,
+    NavigableString,
+    PageElement,
+    ProcessingInstruction,
+    ResultSet,
+    SoupStrainer,
+    Tag,
+    )
+
+# The very first thing we do is give a useful error if someone is
+# running this code under Python 3 without converting it.
+'You are trying to run the Python 2 version of Beautiful Soup under Python 3. This will not work.'!='You need to convert the code, either by installing it (`python setup.py install`) or by running 2to3 (`2to3 -w bs4`).'
+
+class BeautifulSoup(Tag):
+    """
+    This class defines the basic interface called by the tree builders.
+
+    These methods will be called by the parser:
+      reset()
+      feed(markup)
+
+    The tree builder may call these methods from its feed() implementation:
+      handle_starttag(name, attrs) # See note about return value
+      handle_endtag(name)
+      handle_data(data) # Appends to the current data node
+      endData(containerClass=NavigableString) # Ends the current data node
+
+    No matter how complicated the underlying parser is, you should be
+    able to build a tree using 'start tag' events, 'end tag' events,
+    'data' events, and "done with data" events.
+
+    If you encounter an empty-element tag (aka a self-closing tag,
+    like HTML's <br> tag), call handle_starttag and then
+    handle_endtag.
+    """
+    ROOT_TAG_NAME = '[document]'
+
+    # If the end-user gives no indication which tree builder they
+    # want, look for one with these features.
+    DEFAULT_BUILDER_FEATURES = ['html', 'fast']
+
+    ASCII_SPACES = '\x20\x0a\x09\x0c\x0d'
+
+    NO_PARSER_SPECIFIED_WARNING = "No parser was explicitly specified, so I'm using the best available %(markup_type)s parser for this system (\"%(parser)s\"). This usually isn't a problem, but if you run this code on another system, or in a different virtual environment, it may use a different parser and behave differently.\n\nThe code that caused this warning is on line %(line_number)s of the file %(filename)s. To get rid of this warning, pass the additional argument 'features=\"%(parser)s\"' to the BeautifulSoup constructor.\n"
+
+    def __init__(self, markup="", features=None, builder=None,
+                 parse_only=None, from_encoding=None, exclude_encodings=None,
+                 **kwargs):
+        """Constructor.
+
+        :param markup: A string or a file-like object representing
+        markup to be parsed.
+
+        :param features: Desirable features of the parser to be used. This
+        may be the name of a specific parser ("lxml", "lxml-xml",
+        "html.parser", or "html5lib") or it may be the type of markup
+        to be used ("html", "html5", "xml"). It's recommended that you
+        name a specific parser, so that Beautiful Soup gives you the
+        same results across platforms and virtual environments.
+
+        :param builder: A TreeBuilder subclass to instantiate (or
+        instance to use) instead of looking one up based on
+        `features`. You only need to use this if you've implemented a
+        custom TreeBuilder.
+
+        :param parse_only: A SoupStrainer. Only parts of the document
+        matching the SoupStrainer will be considered. This is useful
+        when parsing part of a document that would otherwise be too
+        large to fit into memory.
+
+        :param from_encoding: A string indicating the encoding of the
+        document to be parsed. Pass this in if Beautiful Soup is
+        guessing wrongly about the document's encoding.
+
+        :param exclude_encodings: A list of strings indicating
+        encodings known to be wrong. Pass this in if you don't know
+        the document's encoding but you know Beautiful Soup's guess is
+        wrong.
+
+        :param kwargs: For backwards compatibility purposes, the
+        constructor accepts certain keyword arguments used in
+        Beautiful Soup 3. None of these arguments do anything in
+        Beautiful Soup 4; they will result in a warning and then be ignored.
+
+        Apart from this, any keyword arguments passed into the BeautifulSoup
+        constructor are propagated to the TreeBuilder constructor. This
+        makes it possible to configure a TreeBuilder beyond saying
+        which one to use.
+
+        """
+
+        if 'convertEntities' in kwargs:
+            del kwargs['convertEntities']
+            warnings.warn(
+                "BS4 does not respect the convertEntities argument to the "
+                "BeautifulSoup constructor. Entities are always converted "
+                "to Unicode characters.")
+
+        if 'markupMassage' in kwargs:
+            del kwargs['markupMassage']
+            warnings.warn(
+                "BS4 does not respect the markupMassage argument to the "
+                "BeautifulSoup constructor. The tree builder is responsible "
+                "for any necessary markup massage.")
+
+        if 'smartQuotesTo' in kwargs:
+            del kwargs['smartQuotesTo']
+            warnings.warn(
+                "BS4 does not respect the smartQuotesTo argument to the "
+                "BeautifulSoup constructor. Smart quotes are always converted "
+                "to Unicode characters.")
+
+        if 'selfClosingTags' in kwargs:
+            del kwargs['selfClosingTags']
+            warnings.warn(
+                "BS4 does not respect the selfClosingTags argument to the "
+                "BeautifulSoup constructor. The tree builder is responsible "
+                "for understanding self-closing tags.")
+
+        if 'isHTML' in kwargs:
+            del kwargs['isHTML']
+            warnings.warn(
+                "BS4 does not respect the isHTML argument to the "
+                "BeautifulSoup constructor. Suggest you use "
+                "features='lxml' for HTML and features='lxml-xml' for "
+                "XML.")
+
+        def deprecated_argument(old_name, new_name):
+            if old_name in kwargs:
+                warnings.warn(
+                    'The "%s" argument to the BeautifulSoup constructor '
+                    'has been renamed to "%s."' % (old_name, new_name))
+                value = kwargs[old_name]
+                del kwargs[old_name]
+                return value
+            return None
+
+        parse_only = parse_only or deprecated_argument(
+            "parseOnlyThese", "parse_only")
+
+        from_encoding = from_encoding or deprecated_argument(
+            "fromEncoding", "from_encoding")
+
+        if from_encoding and isinstance(markup, str):
+            warnings.warn("You provided Unicode markup but also provided a value for from_encoding. Your from_encoding will be ignored.")
+            from_encoding = None
+
+        # We need this information to track whether or not the builder
+        # was specified well enough that we can omit the 'you need to
+        # specify a parser' warning.
+        original_builder = builder
+        original_features = features
+            
+        if isinstance(builder, type):
+            # A builder class was passed in; it needs to be instantiated.
+            builder_class = builder
+            builder = None
+        elif builder is None:
+            if isinstance(features, str):
+                features = [features]
+            if features is None or len(features) == 0:
+                features = self.DEFAULT_BUILDER_FEATURES
+            builder_class = builder_registry.lookup(*features)
+            if builder_class is None:
+                raise FeatureNotFound(
+                    "Couldn't find a tree builder with the features you "
+                    "requested: %s. Do you need to install a parser library?"
+                    % ",".join(features))
+
+        # At this point either we have a TreeBuilder instance in
+        # builder, or we have a builder_class that we can instantiate
+        # with the remaining **kwargs.
+        if builder is None:
+            builder = builder_class(**kwargs)
+            if not original_builder and not (
+                    original_features == builder.NAME or
+                    original_features in builder.ALTERNATE_NAMES
+            ):
+                if builder.is_xml:
+                    markup_type = "XML"
+                else:
+                    markup_type = "HTML"
+
+                # This code adapted from warnings.py so that we get the same line
+                # of code as our warnings.warn() call gets, even if the answer is wrong
+                # (as it may be in a multithreading situation).
+                caller = None
+                try:
+                    caller = sys._getframe(1)
+                except ValueError:
+                    pass
+                if caller:
+                    globals = caller.f_globals
+                    line_number = caller.f_lineno
+                else:
+                    globals = sys.__dict__
+                    line_number= 1                    
+                filename = globals.get('__file__')
+                if filename:
+                    fnl = filename.lower()
+                    if fnl.endswith((".pyc", ".pyo")):
+                        filename = filename[:-1]
+                if filename:
+                    # If there is no filename at all, the user is most likely in a REPL,
+                    # and the warning is not necessary.
+                    values = dict(
+                        filename=filename,
+                        line_number=line_number,
+                        parser=builder.NAME,
+                        markup_type=markup_type
+                    )
+                    warnings.warn(self.NO_PARSER_SPECIFIED_WARNING % values, stacklevel=2)
+        else:
+            if kwargs:
+                warnings.warn("Keyword arguments to the BeautifulSoup constructor will be ignored. These would normally be passed into the TreeBuilder constructor, but a TreeBuilder instance was passed in as `builder`.")
+                    
+        self.builder = builder
+        self.is_xml = builder.is_xml
+        self.known_xml = self.is_xml
+        self._namespaces = dict()
+        self.parse_only = parse_only
+
+        self.builder.initialize_soup(self)
+
+        if hasattr(markup, 'read'):        # It's a file-type object.
+            markup = markup.read()
+        elif len(markup) <= 256 and (
+                (isinstance(markup, bytes) and not b'<' in markup)
+                or (isinstance(markup, str) and not '<' in markup)
+        ):
+            # Print out warnings for a couple beginner problems
+            # involving passing non-markup to Beautiful Soup.
+            # Beautiful Soup will still parse the input as markup,
+            # just in case that's what the user really wants.
+            if (isinstance(markup, str)
+                and not os.path.supports_unicode_filenames):
+                possible_filename = markup.encode("utf8")
+            else:
+                possible_filename = markup
+            is_file = False
+            try:
+                is_file = os.path.exists(possible_filename)
+            except Exception as e:
+                # This is almost certainly a problem involving
+                # characters not valid in filenames on this
+                # system. Just let it go.
+                pass
+            if is_file:
+                if isinstance(markup, str):
+                    markup = markup.encode("utf8")
+                warnings.warn(
+                    '"%s" looks like a filename, not markup. You should'
+                    ' probably open this file and pass the filehandle into'
+                    ' Beautiful Soup.' % markup)
+            self._check_markup_is_url(markup)
+
+        for (self.markup, self.original_encoding, self.declared_html_encoding,
+         self.contains_replacement_characters) in (
+             self.builder.prepare_markup(
+                 markup, from_encoding, exclude_encodings=exclude_encodings)):
+            self.reset()
+            try:
+                self._feed()
+                break
+            except ParserRejectedMarkup:
+                pass
+
+        # Clear out the markup and remove the builder's circular
+        # reference to this object.
+        self.markup = None
+        self.builder.soup = None
+
+    def __copy__(self):
+        copy = type(self)(
+            self.encode('utf-8'), builder=self.builder, from_encoding='utf-8'
+        )
+
+        # Although we encoded the tree to UTF-8, that may not have
+        # been the encoding of the original markup. Set the copy's
+        # .original_encoding to reflect the original object's
+        # .original_encoding.
+        copy.original_encoding = self.original_encoding
+        return copy
+
+    def __getstate__(self):
+        # Frequently a tree builder can't be pickled.
+        d = dict(self.__dict__)
+        if 'builder' in d and not self.builder.picklable:
+            d['builder'] = None
+        return d
+
+    @staticmethod
+    def _check_markup_is_url(markup):
+        """ 
+        Check if markup looks like it's actually a url and raise a warning 
+        if so. Markup can be unicode or str (py2) / bytes (py3).
+        """
+        if isinstance(markup, bytes):
+            space = b' '
+            cant_start_with = (b"http:", b"https:")
+        elif isinstance(markup, str):
+            space = ' '
+            cant_start_with = ("http:", "https:")
+        else:
+            return
+
+        if any(markup.startswith(prefix) for prefix in cant_start_with):
+            if not space in markup:
+                if isinstance(markup, bytes):
+                    decoded_markup = markup.decode('utf-8', 'replace')
+                else:
+                    decoded_markup = markup
+                warnings.warn(
+                    '"%s" looks like a URL. Beautiful Soup is not an'
+                    ' HTTP client. You should probably use an HTTP client like'
+                    ' requests to get the document behind the URL, and feed'
+                    ' that document to Beautiful Soup.' % decoded_markup
+                )
+
+    def _feed(self):
+        # Convert the document to Unicode.
+        self.builder.reset()
+
+        self.builder.feed(self.markup)
+        # Close out any unfinished strings and close all the open tags.
+        self.endData()
+        while self.currentTag.name != self.ROOT_TAG_NAME:
+            self.popTag()
+
+    def reset(self):
+        Tag.__init__(self, self, self.builder, self.ROOT_TAG_NAME)
+        self.hidden = 1
+        self.builder.reset()
+        self.current_data = []
+        self.currentTag = None
+        self.tagStack = []
+        self.preserve_whitespace_tag_stack = []
+        self.pushTag(self)
+
+    def new_tag(self, name, namespace=None, nsprefix=None, attrs={}, **kwattrs):
+        """Create a new tag associated with this soup."""
+        kwattrs.update(attrs)
+        return Tag(None, self.builder, name, namespace, nsprefix, kwattrs)
+
+    def new_string(self, s, subclass=NavigableString):
+        """Create a new NavigableString associated with this soup."""
+        return subclass(s)
+
+    def insert_before(self, successor):
+        raise NotImplementedError("BeautifulSoup objects don't support insert_before().")
+
+    def insert_after(self, successor):
+        raise NotImplementedError("BeautifulSoup objects don't support insert_after().")
+
+    def popTag(self):
+        tag = self.tagStack.pop()
+        if self.preserve_whitespace_tag_stack and tag == self.preserve_whitespace_tag_stack[-1]:
+            self.preserve_whitespace_tag_stack.pop()
+        #print "Pop", tag.name
+        if self.tagStack:
+            self.currentTag = self.tagStack[-1]
+        return self.currentTag
+
+    def pushTag(self, tag):
+        #print "Push", tag.name
+        if self.currentTag is not None:
+            self.currentTag.contents.append(tag)
+        self.tagStack.append(tag)
+        self.currentTag = self.tagStack[-1]
+        if tag.name in self.builder.preserve_whitespace_tags:
+            self.preserve_whitespace_tag_stack.append(tag)
+
+    def endData(self, containerClass=NavigableString):
+        if self.current_data:
+            current_data = ''.join(self.current_data)
+            # If whitespace is not preserved, and this string contains
+            # nothing but ASCII spaces, replace it with a single space
+            # or newline.
+            if not self.preserve_whitespace_tag_stack:
+                strippable = True
+                for i in current_data:
+                    if i not in self.ASCII_SPACES:
+                        strippable = False
+                        break
+                if strippable:
+                    if '\n' in current_data:
+                        current_data = '\n'
+                    else:
+                        current_data = ' '
+
+            # Reset the data collector.
+            self.current_data = []
+
+            # Should we add this string to the tree at all?
+            if self.parse_only and len(self.tagStack) <= 1 and \
+                   (not self.parse_only.text or \
+                    not self.parse_only.search(current_data)):
+                return
+
+            o = containerClass(current_data)
+            self.object_was_parsed(o)
+
+    def object_was_parsed(self, o, parent=None, most_recent_element=None):
+        """Add an object to the parse tree."""
+        if parent is None:
+            parent = self.currentTag
+        if most_recent_element is not None:
+            previous_element = most_recent_element
+        else:
+            previous_element = self._most_recent_element
+
+        next_element = previous_sibling = next_sibling = None
+        if isinstance(o, Tag):
+            next_element = o.next_element
+            next_sibling = o.next_sibling
+            previous_sibling = o.previous_sibling
+            if previous_element is None:
+                previous_element = o.previous_element
+
+        fix = parent.next_element is not None
+
+        o.setup(parent, previous_element, next_element, previous_sibling, next_sibling)
+
+        self._most_recent_element = o
+        parent.contents.append(o)
+
+        # Check if we are inserting into an already parsed node.
+        if fix:
+            self._linkage_fixer(parent)
+
+    def _linkage_fixer(self, el):
+        """Make sure linkage of this fragment is sound."""
+
+        first = el.contents[0]
+        child = el.contents[-1]
+        descendant = child
+
+        if child is first and el.parent is not None:
+            # Parent should be linked to first child
+            el.next_element = child
+            # We are no longer linked to whatever this element is
+            prev_el = child.previous_element
+            if prev_el is not None and prev_el is not el:
+                prev_el.next_element = None
+            # First child should be linked to the parent, and no previous siblings.
+            child.previous_element = el
+            child.previous_sibling = None
+
+        # We have no sibling as we've been appended as the last.
+        child.next_sibling = None
+
+        # This index is a tag, dig deeper for a "last descendant"
+        if isinstance(child, Tag) and child.contents:
+            descendant = child._last_descendant(False)
+
+        # As the final step, link last descendant. It should be linked
+        # to the parent's next sibling (if found), else walk up the chain
+        # and find a parent with a sibling. It should have no next sibling.
+        descendant.next_element = None
+        descendant.next_sibling = None
+        target = el
+        while True:
+            if target is None:
+                break
+            elif target.next_sibling is not None:
+                descendant.next_element = target.next_sibling
+                target.next_sibling.previous_element = child
+                break
+            target = target.parent
+
+    def _popToTag(self, name, nsprefix=None, inclusivePop=True):
+        """Pops the tag stack up to and including the most recent
+        instance of the given tag. If inclusivePop is false, pops the tag
+        stack up to but *not* including the most recent instqance of
+        the given tag."""
+        #print "Popping to %s" % name
+        if name == self.ROOT_TAG_NAME:
+            # The BeautifulSoup object itself can never be popped.
+            return
+
+        most_recently_popped = None
+
+        stack_size = len(self.tagStack)
+        for i in range(stack_size - 1, 0, -1):
+            t = self.tagStack[i]
+            if (name == t.name and nsprefix == t.prefix):
+                if inclusivePop:
+                    most_recently_popped = self.popTag()
+                break
+            most_recently_popped = self.popTag()
+
+        return most_recently_popped
+
+    def handle_starttag(self, name, namespace, nsprefix, attrs):
+        """Push a start tag on to the stack.
+
+        If this method returns None, the tag was rejected by the
+        SoupStrainer. You should proceed as if the tag had not occurred
+        in the document. For instance, if this was a self-closing tag,
+        don't call handle_endtag.
+        """
+
+        # print "Start tag %s: %s" % (name, attrs)
+        self.endData()
+
+        if (self.parse_only and len(self.tagStack) <= 1
+            and (self.parse_only.text
+                 or not self.parse_only.search_tag(name, attrs))):
+            return None
+
+        tag = Tag(self, self.builder, name, namespace, nsprefix, attrs,
+                  self.currentTag, self._most_recent_element)
+        if tag is None:
+            return tag
+        if self._most_recent_element is not None:
+            self._most_recent_element.next_element = tag
+        self._most_recent_element = tag
+        self.pushTag(tag)
+        return tag
+
+    def handle_endtag(self, name, nsprefix=None):
+        #print "End tag: " + name
+        self.endData()
+        self._popToTag(name, nsprefix)
+
+    def handle_data(self, data):
+        self.current_data.append(data)
+
+    def decode(self, pretty_print=False,
+               eventual_encoding=DEFAULT_OUTPUT_ENCODING,
+               formatter="minimal"):
+        """Returns a string or Unicode representation of this document.
+        To get Unicode, pass None for encoding."""
+
+        if self.is_xml:
+            # Print the XML declaration
+            encoding_part = ''
+            if eventual_encoding != None:
+                encoding_part = ' encoding="%s"' % eventual_encoding
+            prefix = '<?xml version="1.0"%s?>\n' % encoding_part
+        else:
+            prefix = ''
+        if not pretty_print:
+            indent_level = None
+        else:
+            indent_level = 0
+        return prefix + super(BeautifulSoup, self).decode(
+            indent_level, eventual_encoding, formatter)
+
+# Alias to make it easier to type import: 'from bs4 import _soup'
+_s = BeautifulSoup
+_soup = BeautifulSoup
+
+class BeautifulStoneSoup(BeautifulSoup):
+    """Deprecated interface to an XML parser."""
+
+    def __init__(self, *args, **kwargs):
+        kwargs['features'] = 'xml'
+        warnings.warn(
+            'The BeautifulStoneSoup class is deprecated. Instead of using '
+            'it, pass features="xml" into the BeautifulSoup constructor.')
+        super(BeautifulStoneSoup, self).__init__(*args, **kwargs)
+
+
+class StopParsing(Exception):
+    pass
+
+class FeatureNotFound(ValueError):
+    pass
+
+
+#By default, act as an HTML pretty-printer.
+if __name__ == '__main__':
+    import sys
+    soup = BeautifulSoup(sys.stdin)
+    print(soup.prettify())
diff --git a/libs/bs4/builder/__init__.py b/libs/bs4/builder/__init__.py
new file mode 100644
index 000000000..cc497cf0b
--- /dev/null
+++ b/libs/bs4/builder/__init__.py
@@ -0,0 +1,367 @@
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+from collections import defaultdict
+import itertools
+import sys
+from bs4.element import (
+    CharsetMetaAttributeValue,
+    ContentMetaAttributeValue,
+    nonwhitespace_re
+    )
+
+__all__ = [
+    'HTMLTreeBuilder',
+    'SAXTreeBuilder',
+    'TreeBuilder',
+    'TreeBuilderRegistry',
+    ]
+
+# Some useful features for a TreeBuilder to have.
+FAST = 'fast'
+PERMISSIVE = 'permissive'
+STRICT = 'strict'
+XML = 'xml'
+HTML = 'html'
+HTML_5 = 'html5'
+
+
+class TreeBuilderRegistry(object):
+
+    def __init__(self):
+        self.builders_for_feature = defaultdict(list)
+        self.builders = []
+
+    def register(self, treebuilder_class):
+        """Register a treebuilder based on its advertised features."""
+        for feature in treebuilder_class.features:
+            self.builders_for_feature[feature].insert(0, treebuilder_class)
+        self.builders.insert(0, treebuilder_class)
+
+    def lookup(self, *features):
+        if len(self.builders) == 0:
+            # There are no builders at all.
+            return None
+
+        if len(features) == 0:
+            # They didn't ask for any features. Give them the most
+            # recently registered builder.
+            return self.builders[0]
+
+        # Go down the list of features in order, and eliminate any builders
+        # that don't match every feature.
+        features = list(features)
+        features.reverse()
+        candidates = None
+        candidate_set = None
+        while len(features) > 0:
+            feature = features.pop()
+            we_have_the_feature = self.builders_for_feature.get(feature, [])
+            if len(we_have_the_feature) > 0:
+                if candidates is None:
+                    candidates = we_have_the_feature
+                    candidate_set = set(candidates)
+                else:
+                    # Eliminate any candidates that don't have this feature.
+                    candidate_set = candidate_set.intersection(
+                        set(we_have_the_feature))
+
+        # The only valid candidates are the ones in candidate_set.
+        # Go through the original list of candidates and pick the first one
+        # that's in candidate_set.
+        if candidate_set is None:
+            return None
+        for candidate in candidates:
+            if candidate in candidate_set:
+                return candidate
+        return None
+
+# The BeautifulSoup class will take feature lists from developers and use them
+# to look up builders in this registry.
+builder_registry = TreeBuilderRegistry()
+
+class TreeBuilder(object):
+    """Turn a document into a Beautiful Soup object tree."""
+
+    NAME = "[Unknown tree builder]"
+    ALTERNATE_NAMES = []
+    features = []
+
+    is_xml = False
+    picklable = False
+    empty_element_tags = None # A tag will be considered an empty-element
+                              # tag when and only when it has no contents.
+    
+    # A value for these tag/attribute combinations is a space- or
+    # comma-separated list of CDATA, rather than a single CDATA.
+    DEFAULT_CDATA_LIST_ATTRIBUTES = {}
+
+    DEFAULT_PRESERVE_WHITESPACE_TAGS = set()
+    
+    USE_DEFAULT = object()
+    
+    def __init__(self, multi_valued_attributes=USE_DEFAULT, preserve_whitespace_tags=USE_DEFAULT):
+        """Constructor.
+
+        :param multi_valued_attributes: If this is set to None, the
+        TreeBuilder will not turn any values for attributes like
+        'class' into lists. Setting this do a dictionary will
+        customize this behavior; look at DEFAULT_CDATA_LIST_ATTRIBUTES
+        for an example.
+
+        Internally, these are called "CDATA list attributes", but that
+        probably doesn't make sense to an end-user, so the argument name
+        is `multi_valued_attributes`.
+
+        :param preserve_whitespace_tags:
+        """
+        self.soup = None
+        if multi_valued_attributes is self.USE_DEFAULT:
+            multi_valued_attributes = self.DEFAULT_CDATA_LIST_ATTRIBUTES
+        self.cdata_list_attributes = multi_valued_attributes
+        if preserve_whitespace_tags is self.USE_DEFAULT:
+            preserve_whitespace_tags = self.DEFAULT_PRESERVE_WHITESPACE_TAGS
+        self.preserve_whitespace_tags = preserve_whitespace_tags
+            
+    def initialize_soup(self, soup):
+        """The BeautifulSoup object has been initialized and is now
+        being associated with the TreeBuilder.
+        """
+        self.soup = soup
+        
+    def reset(self):
+        pass
+
+    def can_be_empty_element(self, tag_name):
+        """Might a tag with this name be an empty-element tag?
+
+        The final markup may or may not actually present this tag as
+        self-closing.
+
+        For instance: an HTMLBuilder does not consider a <p> tag to be
+        an empty-element tag (it's not in
+        HTMLBuilder.empty_element_tags). This means an empty <p> tag
+        will be presented as "<p></p>", not "<p />".
+
+        The default implementation has no opinion about which tags are
+        empty-element tags, so a tag will be presented as an
+        empty-element tag if and only if it has no contents.
+        "<foo></foo>" will become "<foo />", and "<foo>bar</foo>" will
+        be left alone.
+        """
+        if self.empty_element_tags is None:
+            return True
+        return tag_name in self.empty_element_tags
+    
+    def feed(self, markup):
+        raise NotImplementedError()
+
+    def prepare_markup(self, markup, user_specified_encoding=None,
+                       document_declared_encoding=None):
+        return markup, None, None, False
+
+    def test_fragment_to_document(self, fragment):
+        """Wrap an HTML fragment to make it look like a document.
+
+        Different parsers do this differently. For instance, lxml
+        introduces an empty <head> tag, and html5lib
+        doesn't. Abstracting this away lets us write simple tests
+        which run HTML fragments through the parser and compare the
+        results against other HTML fragments.
+
+        This method should not be used outside of tests.
+        """
+        return fragment
+
+    def set_up_substitutions(self, tag):
+        return False
+
+    def _replace_cdata_list_attribute_values(self, tag_name, attrs):
+        """Replaces class="foo bar" with class=["foo", "bar"]
+
+        Modifies its input in place.
+        """
+        if not attrs:
+            return attrs
+        if self.cdata_list_attributes:
+            universal = self.cdata_list_attributes.get('*', [])
+            tag_specific = self.cdata_list_attributes.get(
+                tag_name.lower(), None)
+            for attr in list(attrs.keys()):
+                if attr in universal or (tag_specific and attr in tag_specific):
+                    # We have a "class"-type attribute whose string
+                    # value is a whitespace-separated list of
+                    # values. Split it into a list.
+                    value = attrs[attr]
+                    if isinstance(value, str):
+                        values = nonwhitespace_re.findall(value)
+                    else:
+                        # html5lib sometimes calls setAttributes twice
+                        # for the same tag when rearranging the parse
+                        # tree. On the second call the attribute value
+                        # here is already a list.  If this happens,
+                        # leave the value alone rather than trying to
+                        # split it again.
+                        values = value
+                    attrs[attr] = values
+        return attrs
+
+class SAXTreeBuilder(TreeBuilder):
+    """A Beautiful Soup treebuilder that listens for SAX events."""
+
+    def feed(self, markup):
+        raise NotImplementedError()
+
+    def close(self):
+        pass
+
+    def startElement(self, name, attrs):
+        attrs = dict((key[1], value) for key, value in list(attrs.items()))
+        #print "Start %s, %r" % (name, attrs)
+        self.soup.handle_starttag(name, attrs)
+
+    def endElement(self, name):
+        #print "End %s" % name
+        self.soup.handle_endtag(name)
+
+    def startElementNS(self, nsTuple, nodeName, attrs):
+        # Throw away (ns, nodeName) for now.
+        self.startElement(nodeName, attrs)
+
+    def endElementNS(self, nsTuple, nodeName):
+        # Throw away (ns, nodeName) for now.
+        self.endElement(nodeName)
+        #handler.endElementNS((ns, node.nodeName), node.nodeName)
+
+    def startPrefixMapping(self, prefix, nodeValue):
+        # Ignore the prefix for now.
+        pass
+
+    def endPrefixMapping(self, prefix):
+        # Ignore the prefix for now.
+        # handler.endPrefixMapping(prefix)
+        pass
+
+    def characters(self, content):
+        self.soup.handle_data(content)
+
+    def startDocument(self):
+        pass
+
+    def endDocument(self):
+        pass
+
+
+class HTMLTreeBuilder(TreeBuilder):
+    """This TreeBuilder knows facts about HTML.
+
+    Such as which tags are empty-element tags.
+    """
+
+    empty_element_tags = set([
+        # These are from HTML5.
+        'area', 'base', 'br', 'col', 'embed', 'hr', 'img', 'input', 'keygen', 'link', 'menuitem', 'meta', 'param', 'source', 'track', 'wbr',
+        
+        # These are from earlier versions of HTML and are removed in HTML5.
+        'basefont', 'bgsound', 'command', 'frame', 'image', 'isindex', 'nextid', 'spacer'
+    ])
+
+    # The HTML standard defines these as block-level elements. Beautiful
+    # Soup does not treat these elements differently from other elements,
+    # but it may do so eventually, and this information is available if
+    # you need to use it.
+    block_elements = set(["address", "article", "aside", "blockquote", "canvas", "dd", "div", "dl", "dt", "fieldset", "figcaption", "figure", "footer", "form", "h1", "h2", "h3", "h4", "h5", "h6", "header", "hr", "li", "main", "nav", "noscript", "ol", "output", "p", "pre", "section", "table", "tfoot", "ul", "video"])
+    
+    # The HTML standard defines these attributes as containing a
+    # space-separated list of values, not a single value. That is,
+    # class="foo bar" means that the 'class' attribute has two values,
+    # 'foo' and 'bar', not the single value 'foo bar'.  When we
+    # encounter one of these attributes, we will parse its value into
+    # a list of values if possible. Upon output, the list will be
+    # converted back into a string.
+    DEFAULT_CDATA_LIST_ATTRIBUTES = {
+        "*" : ['class', 'accesskey', 'dropzone'],
+        "a" : ['rel', 'rev'],
+        "link" :  ['rel', 'rev'],
+        "td" : ["headers"],
+        "th" : ["headers"],
+        "td" : ["headers"],
+        "form" : ["accept-charset"],
+        "object" : ["archive"],
+
+        # These are HTML5 specific, as are *.accesskey and *.dropzone above.
+        "area" : ["rel"],
+        "icon" : ["sizes"],
+        "iframe" : ["sandbox"],
+        "output" : ["for"],
+        }
+
+    DEFAULT_PRESERVE_WHITESPACE_TAGS = set(['pre', 'textarea'])
+    
+    def set_up_substitutions(self, tag):
+        # We are only interested in <meta> tags
+        if tag.name != 'meta':
+            return False
+
+        http_equiv = tag.get('http-equiv')
+        content = tag.get('content')
+        charset = tag.get('charset')
+
+        # We are interested in <meta> tags that say what encoding the
+        # document was originally in. This means HTML 5-style <meta>
+        # tags that provide the "charset" attribute. It also means
+        # HTML 4-style <meta> tags that provide the "content"
+        # attribute and have "http-equiv" set to "content-type".
+        #
+        # In both cases we will replace the value of the appropriate
+        # attribute with a standin object that can take on any
+        # encoding.
+        meta_encoding = None
+        if charset is not None:
+            # HTML 5 style:
+            # <meta charset="utf8">
+            meta_encoding = charset
+            tag['charset'] = CharsetMetaAttributeValue(charset)
+
+        elif (content is not None and http_equiv is not None
+              and http_equiv.lower() == 'content-type'):
+            # HTML 4 style:
+            # <meta http-equiv="content-type" content="text/html; charset=utf8">
+            tag['content'] = ContentMetaAttributeValue(content)
+
+        return (meta_encoding is not None)
+
+def register_treebuilders_from(module):
+    """Copy TreeBuilders from the given module into this module."""
+    # I'm fairly sure this is not the best way to do this.
+    this_module = sys.modules['bs4.builder']
+    for name in module.__all__:
+        obj = getattr(module, name)
+
+        if issubclass(obj, TreeBuilder):
+            setattr(this_module, name, obj)
+            this_module.__all__.append(name)
+            # Register the builder while we're at it.
+            this_module.builder_registry.register(obj)
+
+class ParserRejectedMarkup(Exception):
+    pass
+
+# Builders are registered in reverse order of priority, so that custom
+# builder registrations will take precedence. In general, we want lxml
+# to take precedence over html5lib, because it's faster. And we only
+# want to use HTMLParser as a last result.
+from . import _htmlparser
+register_treebuilders_from(_htmlparser)
+try:
+    from . import _html5lib
+    register_treebuilders_from(_html5lib)
+except ImportError:
+    # They don't have html5lib installed.
+    pass
+try:
+    from . import _lxml
+    register_treebuilders_from(_lxml)
+except ImportError:
+    # They don't have lxml installed.
+    pass
diff --git a/libs/bs4/builder/_html5lib.py b/libs/bs4/builder/_html5lib.py
new file mode 100644
index 000000000..090bb61a8
--- /dev/null
+++ b/libs/bs4/builder/_html5lib.py
@@ -0,0 +1,426 @@
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+__all__ = [
+    'HTML5TreeBuilder',
+    ]
+
+import warnings
+import re
+from bs4.builder import (
+    PERMISSIVE,
+    HTML,
+    HTML_5,
+    HTMLTreeBuilder,
+    )
+from bs4.element import (
+    NamespacedAttribute,
+    nonwhitespace_re,
+)
+import html5lib
+from html5lib.constants import (
+    namespaces,
+    prefixes,
+    )
+from bs4.element import (
+    Comment,
+    Doctype,
+    NavigableString,
+    Tag,
+    )
+
+try:
+    # Pre-0.99999999
+    from html5lib.treebuilders import _base as treebuilder_base
+    new_html5lib = False
+except ImportError as e:
+    # 0.99999999 and up
+    from html5lib.treebuilders import base as treebuilder_base
+    new_html5lib = True
+
+class HTML5TreeBuilder(HTMLTreeBuilder):
+    """Use html5lib to build a tree."""
+
+    NAME = "html5lib"
+
+    features = [NAME, PERMISSIVE, HTML_5, HTML]
+
+    def prepare_markup(self, markup, user_specified_encoding,
+                       document_declared_encoding=None, exclude_encodings=None):
+        # Store the user-specified encoding for use later on.
+        self.user_specified_encoding = user_specified_encoding
+
+        # document_declared_encoding and exclude_encodings aren't used
+        # ATM because the html5lib TreeBuilder doesn't use
+        # UnicodeDammit.
+        if exclude_encodings:
+            warnings.warn("You provided a value for exclude_encoding, but the html5lib tree builder doesn't support exclude_encoding.")
+        yield (markup, None, None, False)
+
+    # These methods are defined by Beautiful Soup.
+    def feed(self, markup):
+        if self.soup.parse_only is not None:
+            warnings.warn("You provided a value for parse_only, but the html5lib tree builder doesn't support parse_only. The entire document will be parsed.")
+        parser = html5lib.HTMLParser(tree=self.create_treebuilder)
+
+        extra_kwargs = dict()
+        if not isinstance(markup, str):
+            if new_html5lib:
+                extra_kwargs['override_encoding'] = self.user_specified_encoding
+            else:
+                extra_kwargs['encoding'] = self.user_specified_encoding
+        doc = parser.parse(markup, **extra_kwargs)
+
+        # Set the character encoding detected by the tokenizer.
+        if isinstance(markup, str):
+            # We need to special-case this because html5lib sets
+            # charEncoding to UTF-8 if it gets Unicode input.
+            doc.original_encoding = None
+        else:
+            original_encoding = parser.tokenizer.stream.charEncoding[0]
+            if not isinstance(original_encoding, str):
+                # In 0.99999999 and up, the encoding is an html5lib
+                # Encoding object. We want to use a string for compatibility
+                # with other tree builders.
+                original_encoding = original_encoding.name
+            doc.original_encoding = original_encoding
+
+    def create_treebuilder(self, namespaceHTMLElements):
+        self.underlying_builder = TreeBuilderForHtml5lib(
+            namespaceHTMLElements, self.soup)
+        return self.underlying_builder
+
+    def test_fragment_to_document(self, fragment):
+        """See `TreeBuilder`."""
+        return '<html><head></head><body>%s</body></html>' % fragment
+
+
+class TreeBuilderForHtml5lib(treebuilder_base.TreeBuilder):
+
+    def __init__(self, namespaceHTMLElements, soup=None):
+        if soup:
+            self.soup = soup
+        else:
+            from bs4 import BeautifulSoup
+            self.soup = BeautifulSoup("", "html.parser")
+        super(TreeBuilderForHtml5lib, self).__init__(namespaceHTMLElements)
+
+    def documentClass(self):
+        self.soup.reset()
+        return Element(self.soup, self.soup, None)
+
+    def insertDoctype(self, token):
+        name = token["name"]
+        publicId = token["publicId"]
+        systemId = token["systemId"]
+
+        doctype = Doctype.for_name_and_ids(name, publicId, systemId)
+        self.soup.object_was_parsed(doctype)
+
+    def elementClass(self, name, namespace):
+        tag = self.soup.new_tag(name, namespace)
+        return Element(tag, self.soup, namespace)
+
+    def commentClass(self, data):
+        return TextNode(Comment(data), self.soup)
+
+    def fragmentClass(self):
+        from bs4 import BeautifulSoup
+        self.soup = BeautifulSoup("", "html.parser")
+        self.soup.name = "[document_fragment]"
+        return Element(self.soup, self.soup, None)
+
+    def appendChild(self, node):
+        # XXX This code is not covered by the BS4 tests.
+        self.soup.append(node.element)
+
+    def getDocument(self):
+        return self.soup
+
+    def getFragment(self):
+        return treebuilder_base.TreeBuilder.getFragment(self).element
+
+    def testSerializer(self, element):
+        from bs4 import BeautifulSoup
+        rv = []
+        doctype_re = re.compile(r'^(.*?)(?: PUBLIC "(.*?)"(?: "(.*?)")?| SYSTEM "(.*?)")?$')
+
+        def serializeElement(element, indent=0):
+            if isinstance(element, BeautifulSoup):
+                pass
+            if isinstance(element, Doctype):
+                m = doctype_re.match(element)
+                if m:
+                    name = m.group(1)
+                    if m.lastindex > 1:
+                        publicId = m.group(2) or ""
+                        systemId = m.group(3) or m.group(4) or ""
+                        rv.append("""|%s<!DOCTYPE %s "%s" "%s">""" %
+                                  (' ' * indent, name, publicId, systemId))
+                    else:
+                        rv.append("|%s<!DOCTYPE %s>" % (' ' * indent, name))
+                else:
+                    rv.append("|%s<!DOCTYPE >" % (' ' * indent,))
+            elif isinstance(element, Comment):
+                rv.append("|%s<!-- %s -->" % (' ' * indent, element))
+            elif isinstance(element, NavigableString):
+                rv.append("|%s\"%s\"" % (' ' * indent, element))
+            else:
+                if element.namespace:
+                    name = "%s %s" % (prefixes[element.namespace],
+                                      element.name)
+                else:
+                    name = element.name
+                rv.append("|%s<%s>" % (' ' * indent, name))
+                if element.attrs:
+                    attributes = []
+                    for name, value in list(element.attrs.items()):
+                        if isinstance(name, NamespacedAttribute):
+                            name = "%s %s" % (prefixes[name.namespace], name.name)
+                        if isinstance(value, list):
+                            value = " ".join(value)
+                        attributes.append((name, value))
+
+                    for name, value in sorted(attributes):
+                        rv.append('|%s%s="%s"' % (' ' * (indent + 2), name, value))
+                indent += 2
+                for child in element.children:
+                    serializeElement(child, indent)
+        serializeElement(element, 0)
+
+        return "\n".join(rv)
+
+class AttrList(object):
+    def __init__(self, element):
+        self.element = element
+        self.attrs = dict(self.element.attrs)
+    def __iter__(self):
+        return list(self.attrs.items()).__iter__()
+    def __setitem__(self, name, value):
+        # If this attribute is a multi-valued attribute for this element,
+        # turn its value into a list.
+        list_attr = self.element.cdata_list_attributes
+        if (name in list_attr['*']
+            or (self.element.name in list_attr
+                and name in list_attr[self.element.name])):
+            # A node that is being cloned may have already undergone
+            # this procedure.
+            if not isinstance(value, list):
+                value = nonwhitespace_re.findall(value)
+        self.element[name] = value
+    def items(self):
+        return list(self.attrs.items())
+    def keys(self):
+        return list(self.attrs.keys())
+    def __len__(self):
+        return len(self.attrs)
+    def __getitem__(self, name):
+        return self.attrs[name]
+    def __contains__(self, name):
+        return name in list(self.attrs.keys())
+
+
+class Element(treebuilder_base.Node):
+    def __init__(self, element, soup, namespace):
+        treebuilder_base.Node.__init__(self, element.name)
+        self.element = element
+        self.soup = soup
+        self.namespace = namespace
+
+    def appendChild(self, node):
+        string_child = child = None
+        if isinstance(node, str):
+            # Some other piece of code decided to pass in a string
+            # instead of creating a TextElement object to contain the
+            # string.
+            string_child = child = node
+        elif isinstance(node, Tag):
+            # Some other piece of code decided to pass in a Tag
+            # instead of creating an Element object to contain the
+            # Tag.
+            child = node
+        elif node.element.__class__ == NavigableString:
+            string_child = child = node.element
+            node.parent = self
+        else:
+            child = node.element
+            node.parent = self
+
+        if not isinstance(child, str) and child.parent is not None:
+            node.element.extract()
+
+        if (string_child is not None and self.element.contents
+            and self.element.contents[-1].__class__ == NavigableString):
+            # We are appending a string onto another string.
+            # TODO This has O(n^2) performance, for input like
+            # "a</a>a</a>a</a>..."
+            old_element = self.element.contents[-1]
+            new_element = self.soup.new_string(old_element + string_child)
+            old_element.replace_with(new_element)
+            self.soup._most_recent_element = new_element
+        else:
+            if isinstance(node, str):
+                # Create a brand new NavigableString from this string.
+                child = self.soup.new_string(node)
+
+            # Tell Beautiful Soup to act as if it parsed this element
+            # immediately after the parent's last descendant. (Or
+            # immediately after the parent, if it has no children.)
+            if self.element.contents:
+                most_recent_element = self.element._last_descendant(False)
+            elif self.element.next_element is not None:
+                # Something from further ahead in the parse tree is
+                # being inserted into this earlier element. This is
+                # very annoying because it means an expensive search
+                # for the last element in the tree.
+                most_recent_element = self.soup._last_descendant()
+            else:
+                most_recent_element = self.element
+
+            self.soup.object_was_parsed(
+                child, parent=self.element,
+                most_recent_element=most_recent_element)
+
+    def getAttributes(self):
+        if isinstance(self.element, Comment):
+            return {}
+        return AttrList(self.element)
+
+    def setAttributes(self, attributes):
+
+        if attributes is not None and len(attributes) > 0:
+
+            converted_attributes = []
+            for name, value in list(attributes.items()):
+                if isinstance(name, tuple):
+                    new_name = NamespacedAttribute(*name)
+                    del attributes[name]
+                    attributes[new_name] = value
+
+            self.soup.builder._replace_cdata_list_attribute_values(
+                self.name, attributes)
+            for name, value in list(attributes.items()):
+                self.element[name] = value
+
+            # The attributes may contain variables that need substitution.
+            # Call set_up_substitutions manually.
+            #
+            # The Tag constructor called this method when the Tag was created,
+            # but we just set/changed the attributes, so call it again.
+            self.soup.builder.set_up_substitutions(self.element)
+    attributes = property(getAttributes, setAttributes)
+
+    def insertText(self, data, insertBefore=None):
+        text = TextNode(self.soup.new_string(data), self.soup)
+        if insertBefore:
+            self.insertBefore(text, insertBefore)
+        else:
+            self.appendChild(text)
+
+    def insertBefore(self, node, refNode):
+        index = self.element.index(refNode.element)
+        if (node.element.__class__ == NavigableString and self.element.contents
+            and self.element.contents[index-1].__class__ == NavigableString):
+            # (See comments in appendChild)
+            old_node = self.element.contents[index-1]
+            new_str = self.soup.new_string(old_node + node.element)
+            old_node.replace_with(new_str)
+        else:
+            self.element.insert(index, node.element)
+            node.parent = self
+
+    def removeChild(self, node):
+        node.element.extract()
+
+    def reparentChildren(self, new_parent):
+        """Move all of this tag's children into another tag."""
+        # print "MOVE", self.element.contents
+        # print "FROM", self.element
+        # print "TO", new_parent.element
+
+        element = self.element
+        new_parent_element = new_parent.element
+        # Determine what this tag's next_element will be once all the children
+        # are removed.
+        final_next_element = element.next_sibling
+
+        new_parents_last_descendant = new_parent_element._last_descendant(False, False)
+        if len(new_parent_element.contents) > 0:
+            # The new parent already contains children. We will be
+            # appending this tag's children to the end.
+            new_parents_last_child = new_parent_element.contents[-1]
+            new_parents_last_descendant_next_element = new_parents_last_descendant.next_element
+        else:
+            # The new parent contains no children.
+            new_parents_last_child = None
+            new_parents_last_descendant_next_element = new_parent_element.next_element
+
+        to_append = element.contents
+        if len(to_append) > 0:
+            # Set the first child's previous_element and previous_sibling
+            # to elements within the new parent
+            first_child = to_append[0]
+            if new_parents_last_descendant is not None:
+                first_child.previous_element = new_parents_last_descendant
+            else:
+                first_child.previous_element = new_parent_element
+            first_child.previous_sibling = new_parents_last_child
+            if new_parents_last_descendant is not None:
+                new_parents_last_descendant.next_element = first_child
+            else:
+                new_parent_element.next_element = first_child
+            if new_parents_last_child is not None:
+                new_parents_last_child.next_sibling = first_child
+
+            # Find the very last element being moved. It is now the
+            # parent's last descendant. It has no .next_sibling and
+            # its .next_element is whatever the previous last
+            # descendant had.
+            last_childs_last_descendant = to_append[-1]._last_descendant(False, True)
+
+            last_childs_last_descendant.next_element = new_parents_last_descendant_next_element
+            if new_parents_last_descendant_next_element is not None:
+                # TODO: This code has no test coverage and I'm not sure
+                # how to get html5lib to go through this path, but it's
+                # just the other side of the previous line.
+                new_parents_last_descendant_next_element.previous_element = last_childs_last_descendant
+            last_childs_last_descendant.next_sibling = None
+
+        for child in to_append:
+            child.parent = new_parent_element
+            new_parent_element.contents.append(child)
+
+        # Now that this element has no children, change its .next_element.
+        element.contents = []
+        element.next_element = final_next_element
+
+        # print "DONE WITH MOVE"
+        # print "FROM", self.element
+        # print "TO", new_parent_element
+
+    def cloneNode(self):
+        tag = self.soup.new_tag(self.element.name, self.namespace)
+        node = Element(tag, self.soup, self.namespace)
+        for key,value in self.attributes:
+            node.attributes[key] = value
+        return node
+
+    def hasContent(self):
+        return self.element.contents
+
+    def getNameTuple(self):
+        if self.namespace == None:
+            return namespaces["html"], self.name
+        else:
+            return self.namespace, self.name
+
+    nameTuple = property(getNameTuple)
+
+class TextNode(Element):
+    def __init__(self, element, soup):
+        treebuilder_base.Node.__init__(self, None)
+        self.element = element
+        self.soup = soup
+
+    def cloneNode(self):
+        raise NotImplementedError
diff --git a/libs/bs4/builder/_htmlparser.py b/libs/bs4/builder/_htmlparser.py
new file mode 100644
index 000000000..ea549c356
--- /dev/null
+++ b/libs/bs4/builder/_htmlparser.py
@@ -0,0 +1,350 @@
+# encoding: utf-8
+"""Use the HTMLParser library to parse HTML files that aren't too bad."""
+
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+__all__ = [
+    'HTMLParserTreeBuilder',
+    ]
+
+from html.parser import HTMLParser
+
+try:
+    from html.parser import HTMLParseError
+except ImportError as e:
+    # HTMLParseError is removed in Python 3.5. Since it can never be
+    # thrown in 3.5, we can just define our own class as a placeholder.
+    class HTMLParseError(Exception):
+        pass
+
+import sys
+import warnings
+
+# Starting in Python 3.2, the HTMLParser constructor takes a 'strict'
+# argument, which we'd like to set to False. Unfortunately,
+# http://bugs.python.org/issue13273 makes strict=True a better bet
+# before Python 3.2.3.
+#
+# At the end of this file, we monkeypatch HTMLParser so that
+# strict=True works well on Python 3.2.2.
+major, minor, release = sys.version_info[:3]
+CONSTRUCTOR_TAKES_STRICT = major == 3 and minor == 2 and release >= 3
+CONSTRUCTOR_STRICT_IS_DEPRECATED = major == 3 and minor == 3
+CONSTRUCTOR_TAKES_CONVERT_CHARREFS = major == 3 and minor >= 4
+
+
+from bs4.element import (
+    CData,
+    Comment,
+    Declaration,
+    Doctype,
+    ProcessingInstruction,
+    )
+from bs4.dammit import EntitySubstitution, UnicodeDammit
+
+from bs4.builder import (
+    HTML,
+    HTMLTreeBuilder,
+    STRICT,
+    )
+
+
+HTMLPARSER = 'html.parser'
+
+class BeautifulSoupHTMLParser(HTMLParser):
+
+    def __init__(self, *args, **kwargs):
+        HTMLParser.__init__(self, *args, **kwargs)
+
+        # Keep a list of empty-element tags that were encountered
+        # without an explicit closing tag. If we encounter a closing tag
+        # of this type, we'll associate it with one of those entries.
+        #
+        # This isn't a stack because we don't care about the
+        # order. It's a list of closing tags we've already handled and
+        # will ignore, assuming they ever show up.
+        self.already_closed_empty_element = []
+
+    def error(self, msg):
+        """In Python 3, HTMLParser subclasses must implement error(), although this
+        requirement doesn't appear to be documented.
+
+        In Python 2, HTMLParser implements error() as raising an exception.
+
+        In any event, this method is called only on very strange markup and our best strategy
+        is to pretend it didn't happen and keep going.
+        """
+        warnings.warn(msg)
+        
+    def handle_startendtag(self, name, attrs):
+        # This is only called when the markup looks like
+        # <tag/>.
+
+        # is_startend() tells handle_starttag not to close the tag
+        # just because its name matches a known empty-element tag. We
+        # know that this is an empty-element tag and we want to call
+        # handle_endtag ourselves.
+        tag = self.handle_starttag(name, attrs, handle_empty_element=False)
+        self.handle_endtag(name)
+        
+    def handle_starttag(self, name, attrs, handle_empty_element=True):
+        # XXX namespace
+        attr_dict = {}
+        for key, value in attrs:
+            # Change None attribute values to the empty string
+            # for consistency with the other tree builders.
+            if value is None:
+                value = ''
+            attr_dict[key] = value
+            attrvalue = '""'
+        #print "START", name
+        tag = self.soup.handle_starttag(name, None, None, attr_dict)
+        if tag and tag.is_empty_element and handle_empty_element:
+            # Unlike other parsers, html.parser doesn't send separate end tag
+            # events for empty-element tags. (It's handled in
+            # handle_startendtag, but only if the original markup looked like
+            # <tag/>.)
+            #
+            # So we need to call handle_endtag() ourselves. Since we
+            # know the start event is identical to the end event, we
+            # don't want handle_endtag() to cross off any previous end
+            # events for tags of this name.
+            self.handle_endtag(name, check_already_closed=False)
+
+            # But we might encounter an explicit closing tag for this tag
+            # later on. If so, we want to ignore it.
+            self.already_closed_empty_element.append(name)
+            
+    def handle_endtag(self, name, check_already_closed=True):
+        #print "END", name
+        if check_already_closed and name in self.already_closed_empty_element:
+            # This is a redundant end tag for an empty-element tag.
+            # We've already called handle_endtag() for it, so just
+            # check it off the list.
+            # print "ALREADY CLOSED", name
+            self.already_closed_empty_element.remove(name)
+        else:
+            self.soup.handle_endtag(name)
+
+    def handle_data(self, data):
+        self.soup.handle_data(data)
+
+    def handle_charref(self, name):
+        # XXX workaround for a bug in HTMLParser. Remove this once
+        # it's fixed in all supported versions.
+        # http://bugs.python.org/issue13633
+        if name.startswith('x'):
+            real_name = int(name.lstrip('x'), 16)
+        elif name.startswith('X'):
+            real_name = int(name.lstrip('X'), 16)
+        else:
+            real_name = int(name)
+
+        data = None
+        if real_name < 256:
+            # HTML numeric entities are supposed to reference Unicode
+            # code points, but sometimes they reference code points in
+            # some other encoding (ahem, Windows-1252). E.g. &#147;
+            # instead of &#201; for LEFT DOUBLE QUOTATION MARK. This
+            # code tries to detect this situation and compensate.
+            for encoding in (self.soup.original_encoding, 'windows-1252'):
+                if not encoding:
+                    continue
+                try:
+                    data = bytearray([real_name]).decode(encoding)
+                except UnicodeDecodeError as e:
+                    pass
+        if not data:
+            try:
+                data = chr(real_name)
+            except (ValueError, OverflowError) as e:
+                pass
+        data = data or "\N{REPLACEMENT CHARACTER}"
+        self.handle_data(data)
+
+    def handle_entityref(self, name):
+        character = EntitySubstitution.HTML_ENTITY_TO_CHARACTER.get(name)
+        if character is not None:
+            data = character
+        else:
+            # If this were XML, it would be ambiguous whether "&foo"
+            # was an character entity reference with a missing
+            # semicolon or the literal string "&foo". Since this is
+            # HTML, we have a complete list of all character entity references,
+            # and this one wasn't found, so assume it's the literal string "&foo".
+            data = "&%s" % name
+        self.handle_data(data)
+
+    def handle_comment(self, data):
+        self.soup.endData()
+        self.soup.handle_data(data)
+        self.soup.endData(Comment)
+
+    def handle_decl(self, data):
+        self.soup.endData()
+        if data.startswith("DOCTYPE "):
+            data = data[len("DOCTYPE "):]
+        elif data == 'DOCTYPE':
+            # i.e. "<!DOCTYPE>"
+            data = ''
+        self.soup.handle_data(data)
+        self.soup.endData(Doctype)
+
+    def unknown_decl(self, data):
+        if data.upper().startswith('CDATA['):
+            cls = CData
+            data = data[len('CDATA['):]
+        else:
+            cls = Declaration
+        self.soup.endData()
+        self.soup.handle_data(data)
+        self.soup.endData(cls)
+
+    def handle_pi(self, data):
+        self.soup.endData()
+        self.soup.handle_data(data)
+        self.soup.endData(ProcessingInstruction)
+
+
+class HTMLParserTreeBuilder(HTMLTreeBuilder):
+
+    is_xml = False
+    picklable = True
+    NAME = HTMLPARSER
+    features = [NAME, HTML, STRICT]
+
+    def __init__(self, parser_args=None, parser_kwargs=None, **kwargs):
+        super(HTMLParserTreeBuilder, self).__init__(**kwargs)
+        parser_args = parser_args or []
+        parser_kwargs = parser_kwargs or {}
+        if CONSTRUCTOR_TAKES_STRICT and not CONSTRUCTOR_STRICT_IS_DEPRECATED:
+            parser_kwargs['strict'] = False
+        if CONSTRUCTOR_TAKES_CONVERT_CHARREFS:
+            parser_kwargs['convert_charrefs'] = False
+        self.parser_args = (parser_args, parser_kwargs)
+
+    def prepare_markup(self, markup, user_specified_encoding=None,
+                       document_declared_encoding=None, exclude_encodings=None):
+        """
+        :return: A 4-tuple (markup, original encoding, encoding
+        declared within markup, whether any characters had to be
+        replaced with REPLACEMENT CHARACTER).
+        """
+        if isinstance(markup, str):
+            yield (markup, None, None, False)
+            return
+
+        try_encodings = [user_specified_encoding, document_declared_encoding]
+        dammit = UnicodeDammit(markup, try_encodings, is_html=True,
+                               exclude_encodings=exclude_encodings)
+        yield (dammit.markup, dammit.original_encoding,
+               dammit.declared_html_encoding,
+               dammit.contains_replacement_characters)
+
+    def feed(self, markup):
+        args, kwargs = self.parser_args
+        parser = BeautifulSoupHTMLParser(*args, **kwargs)
+        parser.soup = self.soup
+        try:
+            parser.feed(markup)
+            parser.close()
+        except HTMLParseError as e:
+            warnings.warn(RuntimeWarning(
+                "Python's built-in HTMLParser cannot parse the given document. This is not a bug in Beautiful Soup. The best solution is to install an external parser (lxml or html5lib), and use Beautiful Soup with that parser. See http://www.crummy.com/software/BeautifulSoup/bs4/doc/#installing-a-parser for help."))
+            raise e
+        parser.already_closed_empty_element = []
+
+# Patch 3.2 versions of HTMLParser earlier than 3.2.3 to use some
+# 3.2.3 code. This ensures they don't treat markup like <p></p> as a
+# string.
+#
+# XXX This code can be removed once most Python 3 users are on 3.2.3.
+if major == 3 and minor == 2 and not CONSTRUCTOR_TAKES_STRICT:
+    import re
+    attrfind_tolerant = re.compile(
+        r'\s*((?<=[\'"\s])[^\s/>][^\s/=>]*)(\s*=+\s*'
+        r'(\'[^\']*\'|"[^"]*"|(?![\'"])[^>\s]*))?')
+    HTMLParserTreeBuilder.attrfind_tolerant = attrfind_tolerant
+
+    locatestarttagend = re.compile(r"""
+  <[a-zA-Z][-.a-zA-Z0-9:_]*          # tag name
+  (?:\s+                             # whitespace before attribute name
+    (?:[a-zA-Z_][-.:a-zA-Z0-9_]*     # attribute name
+      (?:\s*=\s*                     # value indicator
+        (?:'[^']*'                   # LITA-enclosed value
+          |\"[^\"]*\"                # LIT-enclosed value
+          |[^'\">\s]+                # bare value
+         )
+       )?
+     )
+   )*
+  \s*                                # trailing whitespace
+""", re.VERBOSE)
+    BeautifulSoupHTMLParser.locatestarttagend = locatestarttagend
+
+    from html.parser import tagfind, attrfind
+
+    def parse_starttag(self, i):
+        self.__starttag_text = None
+        endpos = self.check_for_whole_start_tag(i)
+        if endpos < 0:
+            return endpos
+        rawdata = self.rawdata
+        self.__starttag_text = rawdata[i:endpos]
+
+        # Now parse the data between i+1 and j into a tag and attrs
+        attrs = []
+        match = tagfind.match(rawdata, i+1)
+        assert match, 'unexpected call to parse_starttag()'
+        k = match.end()
+        self.lasttag = tag = rawdata[i+1:k].lower()
+        while k < endpos:
+            if self.strict:
+                m = attrfind.match(rawdata, k)
+            else:
+                m = attrfind_tolerant.match(rawdata, k)
+            if not m:
+                break
+            attrname, rest, attrvalue = m.group(1, 2, 3)
+            if not rest:
+                attrvalue = None
+            elif attrvalue[:1] == '\'' == attrvalue[-1:] or \
+                 attrvalue[:1] == '"' == attrvalue[-1:]:
+                attrvalue = attrvalue[1:-1]
+            if attrvalue:
+                attrvalue = self.unescape(attrvalue)
+            attrs.append((attrname.lower(), attrvalue))
+            k = m.end()
+
+        end = rawdata[k:endpos].strip()
+        if end not in (">", "/>"):
+            lineno, offset = self.getpos()
+            if "\n" in self.__starttag_text:
+                lineno = lineno + self.__starttag_text.count("\n")
+                offset = len(self.__starttag_text) \
+                         - self.__starttag_text.rfind("\n")
+            else:
+                offset = offset + len(self.__starttag_text)
+            if self.strict:
+                self.error("junk characters in start tag: %r"
+                           % (rawdata[k:endpos][:20],))
+            self.handle_data(rawdata[i:endpos])
+            return endpos
+        if end.endswith('/>'):
+            # XHTML-style empty tag: <span attr="value" />
+            self.handle_startendtag(tag, attrs)
+        else:
+            self.handle_starttag(tag, attrs)
+            if tag in self.CDATA_CONTENT_ELEMENTS:
+                self.set_cdata_mode(tag)
+        return endpos
+
+    def set_cdata_mode(self, elem):
+        self.cdata_elem = elem.lower()
+        self.interesting = re.compile(r'</\s*%s\s*>' % self.cdata_elem, re.I)
+
+    BeautifulSoupHTMLParser.parse_starttag = parse_starttag
+    BeautifulSoupHTMLParser.set_cdata_mode = set_cdata_mode
+
+    CONSTRUCTOR_TAKES_STRICT = True
diff --git a/libs/bs4/builder/_lxml.py b/libs/bs4/builder/_lxml.py
new file mode 100644
index 000000000..a490e2301
--- /dev/null
+++ b/libs/bs4/builder/_lxml.py
@@ -0,0 +1,296 @@
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+__all__ = [
+    'LXMLTreeBuilderForXML',
+    'LXMLTreeBuilder',
+    ]
+
+try:
+    from collections.abc import Callable # Python 3.6
+except ImportError as e:
+    from collections import Callable
+
+from io import BytesIO
+from io import StringIO
+from lxml import etree
+from bs4.element import (
+    Comment,
+    Doctype,
+    NamespacedAttribute,
+    ProcessingInstruction,
+    XMLProcessingInstruction,
+)
+from bs4.builder import (
+    FAST,
+    HTML,
+    HTMLTreeBuilder,
+    PERMISSIVE,
+    ParserRejectedMarkup,
+    TreeBuilder,
+    XML)
+from bs4.dammit import EncodingDetector
+
+LXML = 'lxml'
+
+def _invert(d):
+    "Invert a dictionary."
+    return dict((v,k) for k, v in list(d.items()))
+
+class LXMLTreeBuilderForXML(TreeBuilder):
+    DEFAULT_PARSER_CLASS = etree.XMLParser
+
+    is_xml = True
+    processing_instruction_class = XMLProcessingInstruction
+
+    NAME = "lxml-xml"
+    ALTERNATE_NAMES = ["xml"]
+
+    # Well, it's permissive by XML parser standards.
+    features = [NAME, LXML, XML, FAST, PERMISSIVE]
+
+    CHUNK_SIZE = 512
+
+    # This namespace mapping is specified in the XML Namespace
+    # standard.
+    DEFAULT_NSMAPS = dict(xml='http://www.w3.org/XML/1998/namespace')
+
+    DEFAULT_NSMAPS_INVERTED = _invert(DEFAULT_NSMAPS)
+
+    def initialize_soup(self, soup):
+        """Let the BeautifulSoup object know about the standard namespace
+        mapping.
+        """
+        super(LXMLTreeBuilderForXML, self).initialize_soup(soup)
+        self._register_namespaces(self.DEFAULT_NSMAPS)
+
+    def _register_namespaces(self, mapping):
+        """Let the BeautifulSoup object know about namespaces encountered
+        while parsing the document.
+
+        This might be useful later on when creating CSS selectors.
+        """
+        for key, value in list(mapping.items()):
+            if key and key not in self.soup._namespaces:
+                # Let the BeautifulSoup object know about a new namespace.
+                # If there are multiple namespaces defined with the same
+                # prefix, the first one in the document takes precedence.
+                self.soup._namespaces[key] = value
+
+    def default_parser(self, encoding):
+        # This can either return a parser object or a class, which
+        # will be instantiated with default arguments.
+        if self._default_parser is not None:
+            return self._default_parser
+        return etree.XMLParser(
+            target=self, strip_cdata=False, recover=True, encoding=encoding)
+
+    def parser_for(self, encoding):
+        # Use the default parser.
+        parser = self.default_parser(encoding)
+
+        if isinstance(parser, Callable):
+            # Instantiate the parser with default arguments
+            parser = parser(target=self, strip_cdata=False, encoding=encoding)
+        return parser
+
+    def __init__(self, parser=None, empty_element_tags=None, **kwargs):
+        # TODO: Issue a warning if parser is present but not a
+        # callable, since that means there's no way to create new
+        # parsers for different encodings.
+        self._default_parser = parser
+        if empty_element_tags is not None:
+            self.empty_element_tags = set(empty_element_tags)
+        self.soup = None
+        self.nsmaps = [self.DEFAULT_NSMAPS_INVERTED]
+        super(LXMLTreeBuilderForXML, self).__init__(**kwargs)
+        
+    def _getNsTag(self, tag):
+        # Split the namespace URL out of a fully-qualified lxml tag
+        # name. Copied from lxml's src/lxml/sax.py.
+        if tag[0] == '{':
+            return tuple(tag[1:].split('}', 1))
+        else:
+            return (None, tag)
+
+    def prepare_markup(self, markup, user_specified_encoding=None,
+                       exclude_encodings=None,
+                       document_declared_encoding=None):
+        """
+        :yield: A series of 4-tuples.
+         (markup, encoding, declared encoding,
+          has undergone character replacement)
+
+        Each 4-tuple represents a strategy for parsing the document.
+        """
+        # Instead of using UnicodeDammit to convert the bytestring to
+        # Unicode using different encodings, use EncodingDetector to
+        # iterate over the encodings, and tell lxml to try to parse
+        # the document as each one in turn.
+        is_html = not self.is_xml
+        if is_html:
+            self.processing_instruction_class = ProcessingInstruction
+        else:
+            self.processing_instruction_class = XMLProcessingInstruction
+
+        if isinstance(markup, str):
+            # We were given Unicode. Maybe lxml can parse Unicode on
+            # this system?
+            yield markup, None, document_declared_encoding, False
+
+        if isinstance(markup, str):
+            # No, apparently not. Convert the Unicode to UTF-8 and
+            # tell lxml to parse it as UTF-8.
+            yield (markup.encode("utf8"), "utf8",
+                   document_declared_encoding, False)
+
+        try_encodings = [user_specified_encoding, document_declared_encoding]
+        detector = EncodingDetector(
+            markup, try_encodings, is_html, exclude_encodings)
+        for encoding in detector.encodings:
+            yield (detector.markup, encoding, document_declared_encoding, False)
+
+    def feed(self, markup):
+        if isinstance(markup, bytes):
+            markup = BytesIO(markup)
+        elif isinstance(markup, str):
+            markup = StringIO(markup)
+
+        # Call feed() at least once, even if the markup is empty,
+        # or the parser won't be initialized.
+        data = markup.read(self.CHUNK_SIZE)
+        try:
+            self.parser = self.parser_for(self.soup.original_encoding)
+            self.parser.feed(data)
+            while len(data) != 0:
+                # Now call feed() on the rest of the data, chunk by chunk.
+                data = markup.read(self.CHUNK_SIZE)
+                if len(data) != 0:
+                    self.parser.feed(data)
+            self.parser.close()
+        except (UnicodeDecodeError, LookupError, etree.ParserError) as e:
+            raise ParserRejectedMarkup(str(e))
+
+    def close(self):
+        self.nsmaps = [self.DEFAULT_NSMAPS_INVERTED]
+
+    def start(self, name, attrs, nsmap={}):
+        # Make sure attrs is a mutable dict--lxml may send an immutable dictproxy.
+        attrs = dict(attrs)
+        nsprefix = None
+        # Invert each namespace map as it comes in.
+        if len(nsmap) == 0 and len(self.nsmaps) > 1:
+                # There are no new namespaces for this tag, but
+                # non-default namespaces are in play, so we need a
+                # separate tag stack to know when they end.
+                self.nsmaps.append(None)
+        elif len(nsmap) > 0:
+            # A new namespace mapping has come into play.
+
+            # First, Let the BeautifulSoup object know about it.
+            self._register_namespaces(nsmap)
+
+            # Then, add it to our running list of inverted namespace
+            # mappings.
+            self.nsmaps.append(_invert(nsmap))
+
+            # Also treat the namespace mapping as a set of attributes on the
+            # tag, so we can recreate it later.
+            attrs = attrs.copy()
+            for prefix, namespace in list(nsmap.items()):
+                attribute = NamespacedAttribute(
+                    "xmlns", prefix, "http://www.w3.org/2000/xmlns/")
+                attrs[attribute] = namespace
+
+        # Namespaces are in play. Find any attributes that came in
+        # from lxml with namespaces attached to their names, and
+        # turn then into NamespacedAttribute objects.
+        new_attrs = {}
+        for attr, value in list(attrs.items()):
+            namespace, attr = self._getNsTag(attr)
+            if namespace is None:
+                new_attrs[attr] = value
+            else:
+                nsprefix = self._prefix_for_namespace(namespace)
+                attr = NamespacedAttribute(nsprefix, attr, namespace)
+                new_attrs[attr] = value
+        attrs = new_attrs
+
+        namespace, name = self._getNsTag(name)
+        nsprefix = self._prefix_for_namespace(namespace)
+        self.soup.handle_starttag(name, namespace, nsprefix, attrs)
+
+    def _prefix_for_namespace(self, namespace):
+        """Find the currently active prefix for the given namespace."""
+        if namespace is None:
+            return None
+        for inverted_nsmap in reversed(self.nsmaps):
+            if inverted_nsmap is not None and namespace in inverted_nsmap:
+                return inverted_nsmap[namespace]
+        return None
+
+    def end(self, name):
+        self.soup.endData()
+        completed_tag = self.soup.tagStack[-1]
+        namespace, name = self._getNsTag(name)
+        nsprefix = None
+        if namespace is not None:
+            for inverted_nsmap in reversed(self.nsmaps):
+                if inverted_nsmap is not None and namespace in inverted_nsmap:
+                    nsprefix = inverted_nsmap[namespace]
+                    break
+        self.soup.handle_endtag(name, nsprefix)
+        if len(self.nsmaps) > 1:
+            # This tag, or one of its parents, introduced a namespace
+            # mapping, so pop it off the stack.
+            self.nsmaps.pop()
+
+    def pi(self, target, data):
+        self.soup.endData()
+        self.soup.handle_data(target + ' ' + data)
+        self.soup.endData(self.processing_instruction_class)
+
+    def data(self, content):
+        self.soup.handle_data(content)
+
+    def doctype(self, name, pubid, system):
+        self.soup.endData()
+        doctype = Doctype.for_name_and_ids(name, pubid, system)
+        self.soup.object_was_parsed(doctype)
+
+    def comment(self, content):
+        "Handle comments as Comment objects."
+        self.soup.endData()
+        self.soup.handle_data(content)
+        self.soup.endData(Comment)
+
+    def test_fragment_to_document(self, fragment):
+        """See `TreeBuilder`."""
+        return '<?xml version="1.0" encoding="utf-8"?>\n%s' % fragment
+
+
+class LXMLTreeBuilder(HTMLTreeBuilder, LXMLTreeBuilderForXML):
+
+    NAME = LXML
+    ALTERNATE_NAMES = ["lxml-html"]
+
+    features = ALTERNATE_NAMES + [NAME, HTML, FAST, PERMISSIVE]
+    is_xml = False
+    processing_instruction_class = ProcessingInstruction
+
+    def default_parser(self, encoding):
+        return etree.HTMLParser
+
+    def feed(self, markup):
+        encoding = self.soup.original_encoding
+        try:
+            self.parser = self.parser_for(encoding)
+            self.parser.feed(markup)
+            self.parser.close()
+        except (UnicodeDecodeError, LookupError, etree.ParserError) as e:
+            raise ParserRejectedMarkup(str(e))
+
+
+    def test_fragment_to_document(self, fragment):
+        """See `TreeBuilder`."""
+        return '<html><body>%s</body></html>' % fragment
diff --git a/libs/bs4/dammit.py b/libs/bs4/dammit.py
new file mode 100644
index 000000000..c7ac4d431
--- /dev/null
+++ b/libs/bs4/dammit.py
@@ -0,0 +1,850 @@
+# -*- coding: utf-8 -*-
+"""Beautiful Soup bonus library: Unicode, Dammit
+
+This library converts a bytestream to Unicode through any means
+necessary. It is heavily based on code from Mark Pilgrim's Universal
+Feed Parser. It works best on XML and HTML, but it does not rewrite the
+XML or HTML to reflect a new encoding; that's the tree builder's job.
+"""
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+import codecs
+from html.entities import codepoint2name
+import re
+import logging
+import string
+
+# Import a library to autodetect character encodings.
+chardet_type = None
+try:
+    # First try the fast C implementation.
+    #  PyPI package: cchardet
+    import cchardet
+    def chardet_dammit(s):
+        return cchardet.detect(s)['encoding']
+except ImportError:
+    try:
+        # Fall back to the pure Python implementation
+        #  Debian package: python-chardet
+        #  PyPI package: chardet
+        import chardet
+        def chardet_dammit(s):
+            return chardet.detect(s)['encoding']
+        #import chardet.constants
+        #chardet.constants._debug = 1
+    except ImportError:
+        # No chardet available.
+        def chardet_dammit(s):
+            return None
+
+# Available from http://cjkpython.i18n.org/.
+try:
+    import iconv_codec
+except ImportError:
+    pass
+
+xml_encoding_re = re.compile(
+    '^<\\?.*encoding=[\'"](.*?)[\'"].*\\?>'.encode(), re.I)
+html_meta_re = re.compile(
+    '<\\s*meta[^>]+charset\\s*=\\s*["\']?([^>]*?)[ /;\'">]'.encode(), re.I)
+
+class EntitySubstitution(object):
+
+    """Substitute XML or HTML entities for the corresponding characters."""
+
+    def _populate_class_variables():
+        lookup = {}
+        reverse_lookup = {}
+        characters_for_re = []
+
+        # &apos is an XHTML entity and an HTML 5, but not an HTML 4
+        # entity. We don't want to use it, but we want to recognize it on the way in.
+        #
+        # TODO: Ideally we would be able to recognize all HTML 5 named
+        # entities, but that's a little tricky.
+        extra = [(39, 'apos')]
+        for codepoint, name in list(codepoint2name.items()) + extra:
+            character = chr(codepoint)
+            if codepoint not in (34, 39):
+                # There's no point in turning the quotation mark into
+                # &quot; or the single quote into &apos;, unless it
+                # happens within an attribute value, which is handled
+                # elsewhere.
+                characters_for_re.append(character)
+                lookup[character] = name
+            # But we do want to recognize those entities on the way in and
+            # convert them to Unicode characters.
+            reverse_lookup[name] = character
+        re_definition = "[%s]" % "".join(characters_for_re)
+        return lookup, reverse_lookup, re.compile(re_definition)
+    (CHARACTER_TO_HTML_ENTITY, HTML_ENTITY_TO_CHARACTER,
+     CHARACTER_TO_HTML_ENTITY_RE) = _populate_class_variables()
+
+    CHARACTER_TO_XML_ENTITY = {
+        "'": "apos",
+        '"': "quot",
+        "&": "amp",
+        "<": "lt",
+        ">": "gt",
+        }
+
+    BARE_AMPERSAND_OR_BRACKET = re.compile("([<>]|"
+                                           "&(?!#\\d+;|#x[0-9a-fA-F]+;|\\w+;)"
+                                           ")")
+
+    AMPERSAND_OR_BRACKET = re.compile("([<>&])")
+
+    @classmethod
+    def _substitute_html_entity(cls, matchobj):
+        entity = cls.CHARACTER_TO_HTML_ENTITY.get(matchobj.group(0))
+        return "&%s;" % entity
+
+    @classmethod
+    def _substitute_xml_entity(cls, matchobj):
+        """Used with a regular expression to substitute the
+        appropriate XML entity for an XML special character."""
+        entity = cls.CHARACTER_TO_XML_ENTITY[matchobj.group(0)]
+        return "&%s;" % entity
+
+    @classmethod
+    def quoted_attribute_value(self, value):
+        """Make a value into a quoted XML attribute, possibly escaping it.
+
+         Most strings will be quoted using double quotes.
+
+          Bob's Bar -> "Bob's Bar"
+
+         If a string contains double quotes, it will be quoted using
+         single quotes.
+
+          Welcome to "my bar" -> 'Welcome to "my bar"'
+
+         If a string contains both single and double quotes, the
+         double quotes will be escaped, and the string will be quoted
+         using double quotes.
+
+          Welcome to "Bob's Bar" -> "Welcome to &quot;Bob's bar&quot;
+        """
+        quote_with = '"'
+        if '"' in value:
+            if "'" in value:
+                # The string contains both single and double
+                # quotes.  Turn the double quotes into
+                # entities. We quote the double quotes rather than
+                # the single quotes because the entity name is
+                # "&quot;" whether this is HTML or XML.  If we
+                # quoted the single quotes, we'd have to decide
+                # between &apos; and &squot;.
+                replace_with = "&quot;"
+                value = value.replace('"', replace_with)
+            else:
+                # There are double quotes but no single quotes.
+                # We can use single quotes to quote the attribute.
+                quote_with = "'"
+        return quote_with + value + quote_with
+
+    @classmethod
+    def substitute_xml(cls, value, make_quoted_attribute=False):
+        """Substitute XML entities for special XML characters.
+
+        :param value: A string to be substituted. The less-than sign
+          will become &lt;, the greater-than sign will become &gt;,
+          and any ampersands will become &amp;. If you want ampersands
+          that appear to be part of an entity definition to be left
+          alone, use substitute_xml_containing_entities() instead.
+
+        :param make_quoted_attribute: If True, then the string will be
+         quoted, as befits an attribute value.
+        """
+        # Escape angle brackets and ampersands.
+        value = cls.AMPERSAND_OR_BRACKET.sub(
+            cls._substitute_xml_entity, value)
+
+        if make_quoted_attribute:
+            value = cls.quoted_attribute_value(value)
+        return value
+
+    @classmethod
+    def substitute_xml_containing_entities(
+        cls, value, make_quoted_attribute=False):
+        """Substitute XML entities for special XML characters.
+
+        :param value: A string to be substituted. The less-than sign will
+          become &lt;, the greater-than sign will become &gt;, and any
+          ampersands that are not part of an entity defition will
+          become &amp;.
+
+        :param make_quoted_attribute: If True, then the string will be
+         quoted, as befits an attribute value.
+        """
+        # Escape angle brackets, and ampersands that aren't part of
+        # entities.
+        value = cls.BARE_AMPERSAND_OR_BRACKET.sub(
+            cls._substitute_xml_entity, value)
+
+        if make_quoted_attribute:
+            value = cls.quoted_attribute_value(value)
+        return value
+
+    @classmethod
+    def substitute_html(cls, s):
+        """Replace certain Unicode characters with named HTML entities.
+
+        This differs from data.encode(encoding, 'xmlcharrefreplace')
+        in that the goal is to make the result more readable (to those
+        with ASCII displays) rather than to recover from
+        errors. There's absolutely nothing wrong with a UTF-8 string
+        containg a LATIN SMALL LETTER E WITH ACUTE, but replacing that
+        character with "&eacute;" will make it more readable to some
+        people.
+        """
+        return cls.CHARACTER_TO_HTML_ENTITY_RE.sub(
+            cls._substitute_html_entity, s)
+
+
+class EncodingDetector:
+    """Suggests a number of possible encodings for a bytestring.
+
+    Order of precedence:
+
+    1. Encodings you specifically tell EncodingDetector to try first
+    (the override_encodings argument to the constructor).
+
+    2. An encoding declared within the bytestring itself, either in an
+    XML declaration (if the bytestring is to be interpreted as an XML
+    document), or in a <meta> tag (if the bytestring is to be
+    interpreted as an HTML document.)
+
+    3. An encoding detected through textual analysis by chardet,
+    cchardet, or a similar external library.
+
+    4. UTF-8.
+
+    5. Windows-1252.
+    """
+    def __init__(self, markup, override_encodings=None, is_html=False,
+                 exclude_encodings=None):
+        self.override_encodings = override_encodings or []
+        exclude_encodings = exclude_encodings or []
+        self.exclude_encodings = set([x.lower() for x in exclude_encodings])
+        self.chardet_encoding = None
+        self.is_html = is_html
+        self.declared_encoding = None
+
+        # First order of business: strip a byte-order mark.
+        self.markup, self.sniffed_encoding = self.strip_byte_order_mark(markup)
+
+    def _usable(self, encoding, tried):
+        if encoding is not None:
+            encoding = encoding.lower()
+            if encoding in self.exclude_encodings:
+                return False
+            if encoding not in tried:
+                tried.add(encoding)
+                return True
+        return False
+
+    @property
+    def encodings(self):
+        """Yield a number of encodings that might work for this markup."""
+        tried = set()
+        for e in self.override_encodings:
+            if self._usable(e, tried):
+                yield e
+
+        # Did the document originally start with a byte-order mark
+        # that indicated its encoding?
+        if self._usable(self.sniffed_encoding, tried):
+            yield self.sniffed_encoding
+
+        # Look within the document for an XML or HTML encoding
+        # declaration.
+        if self.declared_encoding is None:
+            self.declared_encoding = self.find_declared_encoding(
+                self.markup, self.is_html)
+        if self._usable(self.declared_encoding, tried):
+            yield self.declared_encoding
+
+        # Use third-party character set detection to guess at the
+        # encoding.
+        if self.chardet_encoding is None:
+            self.chardet_encoding = chardet_dammit(self.markup)
+        if self._usable(self.chardet_encoding, tried):
+            yield self.chardet_encoding
+
+        # As a last-ditch effort, try utf-8 and windows-1252.
+        for e in ('utf-8', 'windows-1252'):
+            if self._usable(e, tried):
+                yield e
+
+    @classmethod
+    def strip_byte_order_mark(cls, data):
+        """If a byte-order mark is present, strip it and return the encoding it implies."""
+        encoding = None
+        if isinstance(data, str):
+            # Unicode data cannot have a byte-order mark.
+            return data, encoding
+        if (len(data) >= 4) and (data[:2] == b'\xfe\xff') \
+               and (data[2:4] != '\x00\x00'):
+            encoding = 'utf-16be'
+            data = data[2:]
+        elif (len(data) >= 4) and (data[:2] == b'\xff\xfe') \
+                 and (data[2:4] != '\x00\x00'):
+            encoding = 'utf-16le'
+            data = data[2:]
+        elif data[:3] == b'\xef\xbb\xbf':
+            encoding = 'utf-8'
+            data = data[3:]
+        elif data[:4] == b'\x00\x00\xfe\xff':
+            encoding = 'utf-32be'
+            data = data[4:]
+        elif data[:4] == b'\xff\xfe\x00\x00':
+            encoding = 'utf-32le'
+            data = data[4:]
+        return data, encoding
+
+    @classmethod
+    def find_declared_encoding(cls, markup, is_html=False, search_entire_document=False):
+        """Given a document, tries to find its declared encoding.
+
+        An XML encoding is declared at the beginning of the document.
+
+        An HTML encoding is declared in a <meta> tag, hopefully near the
+        beginning of the document.
+        """
+        if search_entire_document:
+            xml_endpos = html_endpos = len(markup)
+        else:
+            xml_endpos = 1024
+            html_endpos = max(2048, int(len(markup) * 0.05))
+
+        declared_encoding = None
+        declared_encoding_match = xml_encoding_re.search(markup, endpos=xml_endpos)
+        if not declared_encoding_match and is_html:
+            declared_encoding_match = html_meta_re.search(markup, endpos=html_endpos)
+        if declared_encoding_match is not None:
+            declared_encoding = declared_encoding_match.groups()[0].decode(
+                'ascii', 'replace')
+        if declared_encoding:
+            return declared_encoding.lower()
+        return None
+
+class UnicodeDammit:
+    """A class for detecting the encoding of a *ML document and
+    converting it to a Unicode string. If the source encoding is
+    windows-1252, can replace MS smart quotes with their HTML or XML
+    equivalents."""
+
+    # This dictionary maps commonly seen values for "charset" in HTML
+    # meta tags to the corresponding Python codec names. It only covers
+    # values that aren't in Python's aliases and can't be determined
+    # by the heuristics in find_codec.
+    CHARSET_ALIASES = {"macintosh": "mac-roman",
+                       "x-sjis": "shift-jis"}
+
+    ENCODINGS_WITH_SMART_QUOTES = [
+        "windows-1252",
+        "iso-8859-1",
+        "iso-8859-2",
+        ]
+
+    def __init__(self, markup, override_encodings=[],
+                 smart_quotes_to=None, is_html=False, exclude_encodings=[]):
+        self.smart_quotes_to = smart_quotes_to
+        self.tried_encodings = []
+        self.contains_replacement_characters = False
+        self.is_html = is_html
+        self.log = logging.getLogger(__name__)
+        self.detector = EncodingDetector(
+            markup, override_encodings, is_html, exclude_encodings)
+
+        # Short-circuit if the data is in Unicode to begin with.
+        if isinstance(markup, str) or markup == '':
+            self.markup = markup
+            self.unicode_markup = str(markup)
+            self.original_encoding = None
+            return
+
+        # The encoding detector may have stripped a byte-order mark.
+        # Use the stripped markup from this point on.
+        self.markup = self.detector.markup
+
+        u = None
+        for encoding in self.detector.encodings:
+            markup = self.detector.markup
+            u = self._convert_from(encoding)
+            if u is not None:
+                break
+
+        if not u:
+            # None of the encodings worked. As an absolute last resort,
+            # try them again with character replacement.
+
+            for encoding in self.detector.encodings:
+                if encoding != "ascii":
+                    u = self._convert_from(encoding, "replace")
+                if u is not None:
+                    self.log.warning(
+                            "Some characters could not be decoded, and were "
+                            "replaced with REPLACEMENT CHARACTER."
+                    )
+                    self.contains_replacement_characters = True
+                    break
+
+        # If none of that worked, we could at this point force it to
+        # ASCII, but that would destroy so much data that I think
+        # giving up is better.
+        self.unicode_markup = u
+        if not u:
+            self.original_encoding = None
+
+    def _sub_ms_char(self, match):
+        """Changes a MS smart quote character to an XML or HTML
+        entity, or an ASCII character."""
+        orig = match.group(1)
+        if self.smart_quotes_to == 'ascii':
+            sub = self.MS_CHARS_TO_ASCII.get(orig).encode()
+        else:
+            sub = self.MS_CHARS.get(orig)
+            if type(sub) == tuple:
+                if self.smart_quotes_to == 'xml':
+                    sub = '&#x'.encode() + sub[1].encode() + ';'.encode()
+                else:
+                    sub = '&'.encode() + sub[0].encode() + ';'.encode()
+            else:
+                sub = sub.encode()
+        return sub
+
+    def _convert_from(self, proposed, errors="strict"):
+        proposed = self.find_codec(proposed)
+        if not proposed or (proposed, errors) in self.tried_encodings:
+            return None
+        self.tried_encodings.append((proposed, errors))
+        markup = self.markup
+        # Convert smart quotes to HTML if coming from an encoding
+        # that might have them.
+        if (self.smart_quotes_to is not None
+            and proposed in self.ENCODINGS_WITH_SMART_QUOTES):
+            smart_quotes_re = b"([\x80-\x9f])"
+            smart_quotes_compiled = re.compile(smart_quotes_re)
+            markup = smart_quotes_compiled.sub(self._sub_ms_char, markup)
+
+        try:
+            #print "Trying to convert document to %s (errors=%s)" % (
+            #    proposed, errors)
+            u = self._to_unicode(markup, proposed, errors)
+            self.markup = u
+            self.original_encoding = proposed
+        except Exception as e:
+            #print "That didn't work!"
+            #print e
+            return None
+        #print "Correct encoding: %s" % proposed
+        return self.markup
+
+    def _to_unicode(self, data, encoding, errors="strict"):
+        '''Given a string and its encoding, decodes the string into Unicode.
+        %encoding is a string recognized by encodings.aliases'''
+        return str(data, encoding, errors)
+
+    @property
+    def declared_html_encoding(self):
+        if not self.is_html:
+            return None
+        return self.detector.declared_encoding
+
+    def find_codec(self, charset):
+        value = (self._codec(self.CHARSET_ALIASES.get(charset, charset))
+               or (charset and self._codec(charset.replace("-", "")))
+               or (charset and self._codec(charset.replace("-", "_")))
+               or (charset and charset.lower())
+               or charset
+                )
+        if value:
+            return value.lower()
+        return None
+
+    def _codec(self, charset):
+        if not charset:
+            return charset
+        codec = None
+        try:
+            codecs.lookup(charset)
+            codec = charset
+        except (LookupError, ValueError):
+            pass
+        return codec
+
+
+    # A partial mapping of ISO-Latin-1 to HTML entities/XML numeric entities.
+    MS_CHARS = {b'\x80': ('euro', '20AC'),
+                b'\x81': ' ',
+                b'\x82': ('sbquo', '201A'),
+                b'\x83': ('fnof', '192'),
+                b'\x84': ('bdquo', '201E'),
+                b'\x85': ('hellip', '2026'),
+                b'\x86': ('dagger', '2020'),
+                b'\x87': ('Dagger', '2021'),
+                b'\x88': ('circ', '2C6'),
+                b'\x89': ('permil', '2030'),
+                b'\x8A': ('Scaron', '160'),
+                b'\x8B': ('lsaquo', '2039'),
+                b'\x8C': ('OElig', '152'),
+                b'\x8D': '?',
+                b'\x8E': ('#x17D', '17D'),
+                b'\x8F': '?',
+                b'\x90': '?',
+                b'\x91': ('lsquo', '2018'),
+                b'\x92': ('rsquo', '2019'),
+                b'\x93': ('ldquo', '201C'),
+                b'\x94': ('rdquo', '201D'),
+                b'\x95': ('bull', '2022'),
+                b'\x96': ('ndash', '2013'),
+                b'\x97': ('mdash', '2014'),
+                b'\x98': ('tilde', '2DC'),
+                b'\x99': ('trade', '2122'),
+                b'\x9a': ('scaron', '161'),
+                b'\x9b': ('rsaquo', '203A'),
+                b'\x9c': ('oelig', '153'),
+                b'\x9d': '?',
+                b'\x9e': ('#x17E', '17E'),
+                b'\x9f': ('Yuml', ''),}
+
+    # A parochial partial mapping of ISO-Latin-1 to ASCII. Contains
+    # horrors like stripping diacritical marks to turn á into a, but also
+    # contains non-horrors like turning “ into ".
+    MS_CHARS_TO_ASCII = {
+        b'\x80' : 'EUR',
+        b'\x81' : ' ',
+        b'\x82' : ',',
+        b'\x83' : 'f',
+        b'\x84' : ',,',
+        b'\x85' : '...',
+        b'\x86' : '+',
+        b'\x87' : '++',
+        b'\x88' : '^',
+        b'\x89' : '%',
+        b'\x8a' : 'S',
+        b'\x8b' : '<',
+        b'\x8c' : 'OE',
+        b'\x8d' : '?',
+        b'\x8e' : 'Z',
+        b'\x8f' : '?',
+        b'\x90' : '?',
+        b'\x91' : "'",
+        b'\x92' : "'",
+        b'\x93' : '"',
+        b'\x94' : '"',
+        b'\x95' : '*',
+        b'\x96' : '-',
+        b'\x97' : '--',
+        b'\x98' : '~',
+        b'\x99' : '(TM)',
+        b'\x9a' : 's',
+        b'\x9b' : '>',
+        b'\x9c' : 'oe',
+        b'\x9d' : '?',
+        b'\x9e' : 'z',
+        b'\x9f' : 'Y',
+        b'\xa0' : ' ',
+        b'\xa1' : '!',
+        b'\xa2' : 'c',
+        b'\xa3' : 'GBP',
+        b'\xa4' : '$', #This approximation is especially parochial--this is the
+                       #generic currency symbol.
+        b'\xa5' : 'YEN',
+        b'\xa6' : '|',
+        b'\xa7' : 'S',
+        b'\xa8' : '..',
+        b'\xa9' : '',
+        b'\xaa' : '(th)',
+        b'\xab' : '<<',
+        b'\xac' : '!',
+        b'\xad' : ' ',
+        b'\xae' : '(R)',
+        b'\xaf' : '-',
+        b'\xb0' : 'o',
+        b'\xb1' : '+-',
+        b'\xb2' : '2',
+        b'\xb3' : '3',
+        b'\xb4' : ("'", 'acute'),
+        b'\xb5' : 'u',
+        b'\xb6' : 'P',
+        b'\xb7' : '*',
+        b'\xb8' : ',',
+        b'\xb9' : '1',
+        b'\xba' : '(th)',
+        b'\xbb' : '>>',
+        b'\xbc' : '1/4',
+        b'\xbd' : '1/2',
+        b'\xbe' : '3/4',
+        b'\xbf' : '?',
+        b'\xc0' : 'A',
+        b'\xc1' : 'A',
+        b'\xc2' : 'A',
+        b'\xc3' : 'A',
+        b'\xc4' : 'A',
+        b'\xc5' : 'A',
+        b'\xc6' : 'AE',
+        b'\xc7' : 'C',
+        b'\xc8' : 'E',
+        b'\xc9' : 'E',
+        b'\xca' : 'E',
+        b'\xcb' : 'E',
+        b'\xcc' : 'I',
+        b'\xcd' : 'I',
+        b'\xce' : 'I',
+        b'\xcf' : 'I',
+        b'\xd0' : 'D',
+        b'\xd1' : 'N',
+        b'\xd2' : 'O',
+        b'\xd3' : 'O',
+        b'\xd4' : 'O',
+        b'\xd5' : 'O',
+        b'\xd6' : 'O',
+        b'\xd7' : '*',
+        b'\xd8' : 'O',
+        b'\xd9' : 'U',
+        b'\xda' : 'U',
+        b'\xdb' : 'U',
+        b'\xdc' : 'U',
+        b'\xdd' : 'Y',
+        b'\xde' : 'b',
+        b'\xdf' : 'B',
+        b'\xe0' : 'a',
+        b'\xe1' : 'a',
+        b'\xe2' : 'a',
+        b'\xe3' : 'a',
+        b'\xe4' : 'a',
+        b'\xe5' : 'a',
+        b'\xe6' : 'ae',
+        b'\xe7' : 'c',
+        b'\xe8' : 'e',
+        b'\xe9' : 'e',
+        b'\xea' : 'e',
+        b'\xeb' : 'e',
+        b'\xec' : 'i',
+        b'\xed' : 'i',
+        b'\xee' : 'i',
+        b'\xef' : 'i',
+        b'\xf0' : 'o',
+        b'\xf1' : 'n',
+        b'\xf2' : 'o',
+        b'\xf3' : 'o',
+        b'\xf4' : 'o',
+        b'\xf5' : 'o',
+        b'\xf6' : 'o',
+        b'\xf7' : '/',
+        b'\xf8' : 'o',
+        b'\xf9' : 'u',
+        b'\xfa' : 'u',
+        b'\xfb' : 'u',
+        b'\xfc' : 'u',
+        b'\xfd' : 'y',
+        b'\xfe' : 'b',
+        b'\xff' : 'y',
+        }
+
+    # A map used when removing rogue Windows-1252/ISO-8859-1
+    # characters in otherwise UTF-8 documents.
+    #
+    # Note that \x81, \x8d, \x8f, \x90, and \x9d are undefined in
+    # Windows-1252.
+    WINDOWS_1252_TO_UTF8 = {
+        0x80 : b'\xe2\x82\xac', # €
+        0x82 : b'\xe2\x80\x9a', # ‚
+        0x83 : b'\xc6\x92',     # ƒ
+        0x84 : b'\xe2\x80\x9e', # „
+        0x85 : b'\xe2\x80\xa6', # …
+        0x86 : b'\xe2\x80\xa0', # †
+        0x87 : b'\xe2\x80\xa1', # ‡
+        0x88 : b'\xcb\x86',     # ˆ
+        0x89 : b'\xe2\x80\xb0', # ‰
+        0x8a : b'\xc5\xa0',     # Š
+        0x8b : b'\xe2\x80\xb9', # ‹
+        0x8c : b'\xc5\x92',     # Œ
+        0x8e : b'\xc5\xbd',     # Ž
+        0x91 : b'\xe2\x80\x98', # ‘
+        0x92 : b'\xe2\x80\x99', # ’
+        0x93 : b'\xe2\x80\x9c', # “
+        0x94 : b'\xe2\x80\x9d', # ”
+        0x95 : b'\xe2\x80\xa2', # •
+        0x96 : b'\xe2\x80\x93', # –
+        0x97 : b'\xe2\x80\x94', # —
+        0x98 : b'\xcb\x9c',     # ˜
+        0x99 : b'\xe2\x84\xa2', # ™
+        0x9a : b'\xc5\xa1',     # š
+        0x9b : b'\xe2\x80\xba', # ›
+        0x9c : b'\xc5\x93',     # œ
+        0x9e : b'\xc5\xbe',     # ž
+        0x9f : b'\xc5\xb8',     # Ÿ
+        0xa0 : b'\xc2\xa0',     #  
+        0xa1 : b'\xc2\xa1',     # ¡
+        0xa2 : b'\xc2\xa2',     # ¢
+        0xa3 : b'\xc2\xa3',     # £
+        0xa4 : b'\xc2\xa4',     # ¤
+        0xa5 : b'\xc2\xa5',     # ¥
+        0xa6 : b'\xc2\xa6',     # ¦
+        0xa7 : b'\xc2\xa7',     # §
+        0xa8 : b'\xc2\xa8',     # ¨
+        0xa9 : b'\xc2\xa9',     # ©
+        0xaa : b'\xc2\xaa',     # ª
+        0xab : b'\xc2\xab',     # «
+        0xac : b'\xc2\xac',     # ¬
+        0xad : b'\xc2\xad',     # ­
+        0xae : b'\xc2\xae',     # ®
+        0xaf : b'\xc2\xaf',     # ¯
+        0xb0 : b'\xc2\xb0',     # °
+        0xb1 : b'\xc2\xb1',     # ±
+        0xb2 : b'\xc2\xb2',     # ²
+        0xb3 : b'\xc2\xb3',     # ³
+        0xb4 : b'\xc2\xb4',     # ´
+        0xb5 : b'\xc2\xb5',     # µ
+        0xb6 : b'\xc2\xb6',     # ¶
+        0xb7 : b'\xc2\xb7',     # ·
+        0xb8 : b'\xc2\xb8',     # ¸
+        0xb9 : b'\xc2\xb9',     # ¹
+        0xba : b'\xc2\xba',     # º
+        0xbb : b'\xc2\xbb',     # »
+        0xbc : b'\xc2\xbc',     # ¼
+        0xbd : b'\xc2\xbd',     # ½
+        0xbe : b'\xc2\xbe',     # ¾
+        0xbf : b'\xc2\xbf',     # ¿
+        0xc0 : b'\xc3\x80',     # À
+        0xc1 : b'\xc3\x81',     # Á
+        0xc2 : b'\xc3\x82',     # Â
+        0xc3 : b'\xc3\x83',     # Ã
+        0xc4 : b'\xc3\x84',     # Ä
+        0xc5 : b'\xc3\x85',     # Å
+        0xc6 : b'\xc3\x86',     # Æ
+        0xc7 : b'\xc3\x87',     # Ç
+        0xc8 : b'\xc3\x88',     # È
+        0xc9 : b'\xc3\x89',     # É
+        0xca : b'\xc3\x8a',     # Ê
+        0xcb : b'\xc3\x8b',     # Ë
+        0xcc : b'\xc3\x8c',     # Ì
+        0xcd : b'\xc3\x8d',     # Í
+        0xce : b'\xc3\x8e',     # Î
+        0xcf : b'\xc3\x8f',     # Ï
+        0xd0 : b'\xc3\x90',     # Ð
+        0xd1 : b'\xc3\x91',     # Ñ
+        0xd2 : b'\xc3\x92',     # Ò
+        0xd3 : b'\xc3\x93',     # Ó
+        0xd4 : b'\xc3\x94',     # Ô
+        0xd5 : b'\xc3\x95',     # Õ
+        0xd6 : b'\xc3\x96',     # Ö
+        0xd7 : b'\xc3\x97',     # ×
+        0xd8 : b'\xc3\x98',     # Ø
+        0xd9 : b'\xc3\x99',     # Ù
+        0xda : b'\xc3\x9a',     # Ú
+        0xdb : b'\xc3\x9b',     # Û
+        0xdc : b'\xc3\x9c',     # Ü
+        0xdd : b'\xc3\x9d',     # Ý
+        0xde : b'\xc3\x9e',     # Þ
+        0xdf : b'\xc3\x9f',     # ß
+        0xe0 : b'\xc3\xa0',     # à
+        0xe1 : b'\xa1',         # á
+        0xe2 : b'\xc3\xa2',     # â
+        0xe3 : b'\xc3\xa3',     # ã
+        0xe4 : b'\xc3\xa4',     # ä
+        0xe5 : b'\xc3\xa5',     # å
+        0xe6 : b'\xc3\xa6',     # æ
+        0xe7 : b'\xc3\xa7',     # ç
+        0xe8 : b'\xc3\xa8',     # è
+        0xe9 : b'\xc3\xa9',     # é
+        0xea : b'\xc3\xaa',     # ê
+        0xeb : b'\xc3\xab',     # ë
+        0xec : b'\xc3\xac',     # ì
+        0xed : b'\xc3\xad',     # í
+        0xee : b'\xc3\xae',     # î
+        0xef : b'\xc3\xaf',     # ï
+        0xf0 : b'\xc3\xb0',     # ð
+        0xf1 : b'\xc3\xb1',     # ñ
+        0xf2 : b'\xc3\xb2',     # ò
+        0xf3 : b'\xc3\xb3',     # ó
+        0xf4 : b'\xc3\xb4',     # ô
+        0xf5 : b'\xc3\xb5',     # õ
+        0xf6 : b'\xc3\xb6',     # ö
+        0xf7 : b'\xc3\xb7',     # ÷
+        0xf8 : b'\xc3\xb8',     # ø
+        0xf9 : b'\xc3\xb9',     # ù
+        0xfa : b'\xc3\xba',     # ú
+        0xfb : b'\xc3\xbb',     # û
+        0xfc : b'\xc3\xbc',     # ü
+        0xfd : b'\xc3\xbd',     # ý
+        0xfe : b'\xc3\xbe',     # þ
+        }
+
+    MULTIBYTE_MARKERS_AND_SIZES = [
+        (0xc2, 0xdf, 2), # 2-byte characters start with a byte C2-DF
+        (0xe0, 0xef, 3), # 3-byte characters start with E0-EF
+        (0xf0, 0xf4, 4), # 4-byte characters start with F0-F4
+        ]
+
+    FIRST_MULTIBYTE_MARKER = MULTIBYTE_MARKERS_AND_SIZES[0][0]
+    LAST_MULTIBYTE_MARKER = MULTIBYTE_MARKERS_AND_SIZES[-1][1]
+
+    @classmethod
+    def detwingle(cls, in_bytes, main_encoding="utf8",
+                  embedded_encoding="windows-1252"):
+        """Fix characters from one encoding embedded in some other encoding.
+
+        Currently the only situation supported is Windows-1252 (or its
+        subset ISO-8859-1), embedded in UTF-8.
+
+        The input must be a bytestring. If you've already converted
+        the document to Unicode, you're too late.
+
+        The output is a bytestring in which `embedded_encoding`
+        characters have been converted to their `main_encoding`
+        equivalents.
+        """
+        if embedded_encoding.replace('_', '-').lower() not in (
+            'windows-1252', 'windows_1252'):
+            raise NotImplementedError(
+                "Windows-1252 and ISO-8859-1 are the only currently supported "
+                "embedded encodings.")
+
+        if main_encoding.lower() not in ('utf8', 'utf-8'):
+            raise NotImplementedError(
+                "UTF-8 is the only currently supported main encoding.")
+
+        byte_chunks = []
+
+        chunk_start = 0
+        pos = 0
+        while pos < len(in_bytes):
+            byte = in_bytes[pos]
+            if not isinstance(byte, int):
+                # Python 2.x
+                byte = ord(byte)
+            if (byte >= cls.FIRST_MULTIBYTE_MARKER
+                and byte <= cls.LAST_MULTIBYTE_MARKER):
+                # This is the start of a UTF-8 multibyte character. Skip
+                # to the end.
+                for start, end, size in cls.MULTIBYTE_MARKERS_AND_SIZES:
+                    if byte >= start and byte <= end:
+                        pos += size
+                        break
+            elif byte >= 0x80 and byte in cls.WINDOWS_1252_TO_UTF8:
+                # We found a Windows-1252 character!
+                # Save the string up to this point as a chunk.
+                byte_chunks.append(in_bytes[chunk_start:pos])
+
+                # Now translate the Windows-1252 character into UTF-8
+                # and add it as another, one-byte chunk.
+                byte_chunks.append(cls.WINDOWS_1252_TO_UTF8[byte])
+                pos += 1
+                chunk_start = pos
+            else:
+                # Go on to the next character.
+                pos += 1
+        if chunk_start == 0:
+            # The string is unchanged.
+            return in_bytes
+        else:
+            # Store the final chunk.
+            byte_chunks.append(in_bytes[chunk_start:])
+        return b''.join(byte_chunks)
+
diff --git a/libs/bs4/diagnose.py b/libs/bs4/diagnose.py
new file mode 100644
index 000000000..b5f6e6c8b
--- /dev/null
+++ b/libs/bs4/diagnose.py
@@ -0,0 +1,224 @@
+"""Diagnostic functions, mainly for use when doing tech support."""
+
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+import cProfile
+from io import StringIO
+from html.parser import HTMLParser
+import bs4
+from bs4 import BeautifulSoup, __version__
+from bs4.builder import builder_registry
+
+import os
+import pstats
+import random
+import tempfile
+import time
+import traceback
+import sys
+import cProfile
+
+def diagnose(data):
+    """Diagnostic suite for isolating common problems."""
+    print("Diagnostic running on Beautiful Soup %s" % __version__)
+    print("Python version %s" % sys.version)
+
+    basic_parsers = ["html.parser", "html5lib", "lxml"]
+    for name in basic_parsers:
+        for builder in builder_registry.builders:
+            if name in builder.features:
+                break
+        else:
+            basic_parsers.remove(name)
+            print((
+                "I noticed that %s is not installed. Installing it may help." %
+                name))
+
+    if 'lxml' in basic_parsers:
+        basic_parsers.append("lxml-xml")
+        try:
+            from lxml import etree
+            print("Found lxml version %s" % ".".join(map(str,etree.LXML_VERSION)))
+        except ImportError as e:
+            print (
+                "lxml is not installed or couldn't be imported.")
+
+
+    if 'html5lib' in basic_parsers:
+        try:
+            import html5lib
+            print("Found html5lib version %s" % html5lib.__version__)
+        except ImportError as e:
+            print (
+                "html5lib is not installed or couldn't be imported.")
+
+    if hasattr(data, 'read'):
+        data = data.read()
+    elif data.startswith("http:") or data.startswith("https:"):
+        print('"%s" looks like a URL. Beautiful Soup is not an HTTP client.' % data)
+        print("You need to use some other library to get the document behind the URL, and feed that document to Beautiful Soup.")
+        return
+    else:
+        try:
+            if os.path.exists(data):
+                print('"%s" looks like a filename. Reading data from the file.' % data)
+                with open(data) as fp:
+                    data = fp.read()
+        except ValueError:
+            # This can happen on some platforms when the 'filename' is
+            # too long. Assume it's data and not a filename.
+            pass
+        print()
+
+    for parser in basic_parsers:
+        print("Trying to parse your markup with %s" % parser)
+        success = False
+        try:
+            soup = BeautifulSoup(data, features=parser)
+            success = True
+        except Exception as e:
+            print("%s could not parse the markup." % parser)
+            traceback.print_exc()
+        if success:
+            print("Here's what %s did with the markup:" % parser)
+            print(soup.prettify())
+
+        print("-" * 80)
+
+def lxml_trace(data, html=True, **kwargs):
+    """Print out the lxml events that occur during parsing.
+
+    This lets you see how lxml parses a document when no Beautiful
+    Soup code is running.
+    """
+    from lxml import etree
+    for event, element in etree.iterparse(StringIO(data), html=html, **kwargs):
+        print(("%s, %4s, %s" % (event, element.tag, element.text)))
+
+class AnnouncingParser(HTMLParser):
+    """Announces HTMLParser parse events, without doing anything else."""
+
+    def _p(self, s):
+        print(s)
+
+    def handle_starttag(self, name, attrs):
+        self._p("%s START" % name)
+
+    def handle_endtag(self, name):
+        self._p("%s END" % name)
+
+    def handle_data(self, data):
+        self._p("%s DATA" % data)
+
+    def handle_charref(self, name):
+        self._p("%s CHARREF" % name)
+
+    def handle_entityref(self, name):
+        self._p("%s ENTITYREF" % name)
+
+    def handle_comment(self, data):
+        self._p("%s COMMENT" % data)
+
+    def handle_decl(self, data):
+        self._p("%s DECL" % data)
+
+    def unknown_decl(self, data):
+        self._p("%s UNKNOWN-DECL" % data)
+
+    def handle_pi(self, data):
+        self._p("%s PI" % data)
+
+def htmlparser_trace(data):
+    """Print out the HTMLParser events that occur during parsing.
+
+    This lets you see how HTMLParser parses a document when no
+    Beautiful Soup code is running.
+    """
+    parser = AnnouncingParser()
+    parser.feed(data)
+
+_vowels = "aeiou"
+_consonants = "bcdfghjklmnpqrstvwxyz"
+
+def rword(length=5):
+    "Generate a random word-like string."
+    s = ''
+    for i in range(length):
+        if i % 2 == 0:
+            t = _consonants
+        else:
+            t = _vowels
+        s += random.choice(t)
+    return s
+
+def rsentence(length=4):
+    "Generate a random sentence-like string."
+    return " ".join(rword(random.randint(4,9)) for i in list(range(length)))
+        
+def rdoc(num_elements=1000):
+    """Randomly generate an invalid HTML document."""
+    tag_names = ['p', 'div', 'span', 'i', 'b', 'script', 'table']
+    elements = []
+    for i in range(num_elements):
+        choice = random.randint(0,3)
+        if choice == 0:
+            # New tag.
+            tag_name = random.choice(tag_names)
+            elements.append("<%s>" % tag_name)
+        elif choice == 1:
+            elements.append(rsentence(random.randint(1,4)))
+        elif choice == 2:
+            # Close a tag.
+            tag_name = random.choice(tag_names)
+            elements.append("</%s>" % tag_name)
+    return "<html>" + "\n".join(elements) + "</html>"
+
+def benchmark_parsers(num_elements=100000):
+    """Very basic head-to-head performance benchmark."""
+    print("Comparative parser benchmark on Beautiful Soup %s" % __version__)
+    data = rdoc(num_elements)
+    print("Generated a large invalid HTML document (%d bytes)." % len(data))
+    
+    for parser in ["lxml", ["lxml", "html"], "html5lib", "html.parser"]:
+        success = False
+        try:
+            a = time.time()
+            soup = BeautifulSoup(data, parser)
+            b = time.time()
+            success = True
+        except Exception as e:
+            print("%s could not parse the markup." % parser)
+            traceback.print_exc()
+        if success:
+            print("BS4+%s parsed the markup in %.2fs." % (parser, b-a))
+
+    from lxml import etree
+    a = time.time()
+    etree.HTML(data)
+    b = time.time()
+    print("Raw lxml parsed the markup in %.2fs." % (b-a))
+
+    import html5lib
+    parser = html5lib.HTMLParser()
+    a = time.time()
+    parser.parse(data)
+    b = time.time()
+    print("Raw html5lib parsed the markup in %.2fs." % (b-a))
+
+def profile(num_elements=100000, parser="lxml"):
+
+    filehandle = tempfile.NamedTemporaryFile()
+    filename = filehandle.name
+
+    data = rdoc(num_elements)
+    vars = dict(bs4=bs4, data=data, parser=parser)
+    cProfile.runctx('bs4.BeautifulSoup(data, parser)' , vars, vars, filename)
+
+    stats = pstats.Stats(filename)
+    # stats.strip_dirs()
+    stats.sort_stats("cumulative")
+    stats.print_stats('_html5lib|bs4', 50)
+
+if __name__ == '__main__':
+    diagnose(sys.stdin.read())
diff --git a/libs/bs4/element.py b/libs/bs4/element.py
new file mode 100644
index 000000000..f16b1663e
--- /dev/null
+++ b/libs/bs4/element.py
@@ -0,0 +1,1579 @@
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+try:
+    from collections.abc import Callable # Python 3.6
+except ImportError as e:
+    from collections import Callable
+import re
+import sys
+import warnings
+try:
+    import soupsieve
+except ImportError as e:
+    soupsieve = None
+    warnings.warn(
+        'The soupsieve package is not installed. CSS selectors cannot be used.'
+    )
+
+from bs4.formatter import (
+    Formatter,
+    HTMLFormatter,
+    XMLFormatter,
+)
+
+DEFAULT_OUTPUT_ENCODING = "utf-8"
+PY3K = (sys.version_info[0] > 2)
+
+nonwhitespace_re = re.compile(r"\S+")
+
+# NOTE: This isn't used as of 4.7.0. I'm leaving it for a little bit on
+# the off chance someone imported it for their own use.
+whitespace_re = re.compile(r"\s+")
+
+def _alias(attr):
+    """Alias one attribute name to another for backward compatibility"""
+    @property
+    def alias(self):
+        return getattr(self, attr)
+
+    @alias.setter
+    def alias(self):
+        return setattr(self, attr)
+    return alias
+
+
+class NamespacedAttribute(str):
+
+    def __new__(cls, prefix, name, namespace=None):
+        if name is None:
+            obj = str.__new__(cls, prefix)
+        elif prefix is None:
+            # Not really namespaced.
+            obj = str.__new__(cls, name)
+        else:
+            obj = str.__new__(cls, prefix + ":" + name)
+        obj.prefix = prefix
+        obj.name = name
+        obj.namespace = namespace
+        return obj
+
+class AttributeValueWithCharsetSubstitution(str):
+    """A stand-in object for a character encoding specified in HTML."""
+
+class CharsetMetaAttributeValue(AttributeValueWithCharsetSubstitution):
+    """A generic stand-in for the value of a meta tag's 'charset' attribute.
+
+    When Beautiful Soup parses the markup '<meta charset="utf8">', the
+    value of the 'charset' attribute will be one of these objects.
+    """
+
+    def __new__(cls, original_value):
+        obj = str.__new__(cls, original_value)
+        obj.original_value = original_value
+        return obj
+
+    def encode(self, encoding):
+        return encoding
+
+
+class ContentMetaAttributeValue(AttributeValueWithCharsetSubstitution):
+    """A generic stand-in for the value of a meta tag's 'content' attribute.
+
+    When Beautiful Soup parses the markup:
+     <meta http-equiv="content-type" content="text/html; charset=utf8">
+
+    The value of the 'content' attribute will be one of these objects.
+    """
+
+    CHARSET_RE = re.compile(r"((^|;)\s*charset=)([^;]*)", re.M)
+
+    def __new__(cls, original_value):
+        match = cls.CHARSET_RE.search(original_value)
+        if match is None:
+            # No substitution necessary.
+            return str.__new__(str, original_value)
+
+        obj = str.__new__(cls, original_value)
+        obj.original_value = original_value
+        return obj
+
+    def encode(self, encoding):
+        def rewrite(match):
+            return match.group(1) + encoding
+        return self.CHARSET_RE.sub(rewrite, self.original_value)
+
+    
+class PageElement(object):
+    """Contains the navigational information for some part of the page
+    (either a tag or a piece of text)"""
+   
+    def setup(self, parent=None, previous_element=None, next_element=None,
+              previous_sibling=None, next_sibling=None):
+        """Sets up the initial relations between this element and
+        other elements."""
+        self.parent = parent
+
+        self.previous_element = previous_element
+        if previous_element is not None:
+            self.previous_element.next_element = self
+
+        self.next_element = next_element
+        if self.next_element is not None:
+            self.next_element.previous_element = self
+
+        self.next_sibling = next_sibling
+        if self.next_sibling is not None:
+            self.next_sibling.previous_sibling = self
+
+        if (previous_sibling is None
+            and self.parent is not None and self.parent.contents):
+            previous_sibling = self.parent.contents[-1]
+
+        self.previous_sibling = previous_sibling
+        if previous_sibling is not None:
+            self.previous_sibling.next_sibling = self
+
+    def format_string(self, s, formatter):
+        """Format the given string using the given formatter."""
+        if formatter is None:
+            return s
+        if not isinstance(formatter, Formatter):
+            formatter = self.formatter_for_name(formatter)
+        output = formatter.substitute(s)
+        return output
+
+    def formatter_for_name(self, formatter):
+        """Look up or create a Formatter for the given identifier,
+        if necessary.
+
+        :param formatter: Can be a Formatter object (used as-is), a
+        function (used as the entity substitution hook for an
+        XMLFormatter or HTMLFormatter), or a string (used to look up
+        an XMLFormatter or HTMLFormatter in the appropriate registry.
+        """
+        if isinstance(formatter, Formatter):
+            return formatter
+        if self._is_xml:
+            c = XMLFormatter
+        else:
+            c = HTMLFormatter
+        if callable(formatter):
+            return c(entity_substitution=formatter)
+        return c.REGISTRY[formatter]
+
+    @property
+    def _is_xml(self):
+        """Is this element part of an XML tree or an HTML tree?
+
+        This is used in formatter_for_name, when deciding whether an
+        XMLFormatter or HTMLFormatter is more appropriate. It can be
+        inefficient, but it should be called very rarely.
+        """
+        if self.known_xml is not None:
+            # Most of the time we will have determined this when the
+            # document is parsed.
+            return self.known_xml
+
+        # Otherwise, it's likely that this element was created by
+        # direct invocation of the constructor from within the user's
+        # Python code.
+        if self.parent is None:
+            # This is the top-level object. It should have .known_xml set
+            # from tree creation. If not, take a guess--BS is usually
+            # used on HTML markup.
+            return getattr(self, 'is_xml', False)
+        return self.parent._is_xml
+
+    nextSibling = _alias("next_sibling")  # BS3
+    previousSibling = _alias("previous_sibling")  # BS3
+
+    def replace_with(self, replace_with):
+        if self.parent is None:
+            raise ValueError(
+                "Cannot replace one element with another when the "
+                "element to be replaced is not part of a tree.")
+        if replace_with is self:
+            return
+        if replace_with is self.parent:
+            raise ValueError("Cannot replace a Tag with its parent.")
+        old_parent = self.parent
+        my_index = self.parent.index(self)
+        self.extract()
+        old_parent.insert(my_index, replace_with)
+        return self
+    replaceWith = replace_with  # BS3
+
+    def unwrap(self):
+        my_parent = self.parent
+        if self.parent is None:
+            raise ValueError(
+                "Cannot replace an element with its contents when that"
+                "element is not part of a tree.")
+        my_index = self.parent.index(self)
+        self.extract()
+        for child in reversed(self.contents[:]):
+            my_parent.insert(my_index, child)
+        return self
+    replace_with_children = unwrap
+    replaceWithChildren = unwrap  # BS3
+
+    def wrap(self, wrap_inside):
+        me = self.replace_with(wrap_inside)
+        wrap_inside.append(me)
+        return wrap_inside
+
+    def extract(self):
+        """Destructively rips this element out of the tree."""
+        if self.parent is not None:
+            del self.parent.contents[self.parent.index(self)]
+
+        #Find the two elements that would be next to each other if
+        #this element (and any children) hadn't been parsed. Connect
+        #the two.
+        last_child = self._last_descendant()
+        next_element = last_child.next_element
+
+        if (self.previous_element is not None and
+            self.previous_element is not next_element):
+            self.previous_element.next_element = next_element
+        if next_element is not None and next_element is not self.previous_element:
+            next_element.previous_element = self.previous_element
+        self.previous_element = None
+        last_child.next_element = None
+
+        self.parent = None
+        if (self.previous_sibling is not None
+            and self.previous_sibling is not self.next_sibling):
+            self.previous_sibling.next_sibling = self.next_sibling
+        if (self.next_sibling is not None
+            and self.next_sibling is not self.previous_sibling):
+            self.next_sibling.previous_sibling = self.previous_sibling
+        self.previous_sibling = self.next_sibling = None
+        return self
+
+    def _last_descendant(self, is_initialized=True, accept_self=True):
+        "Finds the last element beneath this object to be parsed."
+        if is_initialized and self.next_sibling is not None:
+            last_child = self.next_sibling.previous_element
+        else:
+            last_child = self
+            while isinstance(last_child, Tag) and last_child.contents:
+                last_child = last_child.contents[-1]
+        if not accept_self and last_child is self:
+            last_child = None
+        return last_child
+    # BS3: Not part of the API!
+    _lastRecursiveChild = _last_descendant
+
+    def insert(self, position, new_child):
+        if new_child is None:
+            raise ValueError("Cannot insert None into a tag.")
+        if new_child is self:
+            raise ValueError("Cannot insert a tag into itself.")
+        if (isinstance(new_child, str)
+            and not isinstance(new_child, NavigableString)):
+            new_child = NavigableString(new_child)
+
+        from bs4 import BeautifulSoup
+        if isinstance(new_child, BeautifulSoup):
+            # We don't want to end up with a situation where one BeautifulSoup
+            # object contains another. Insert the children one at a time.
+            for subchild in list(new_child.contents):
+                self.insert(position, subchild)
+                position += 1
+            return
+        position = min(position, len(self.contents))
+        if hasattr(new_child, 'parent') and new_child.parent is not None:
+            # We're 'inserting' an element that's already one
+            # of this object's children.
+            if new_child.parent is self:
+                current_index = self.index(new_child)
+                if current_index < position:
+                    # We're moving this element further down the list
+                    # of this object's children. That means that when
+                    # we extract this element, our target index will
+                    # jump down one.
+                    position -= 1
+            new_child.extract()
+
+        new_child.parent = self
+        previous_child = None
+        if position == 0:
+            new_child.previous_sibling = None
+            new_child.previous_element = self
+        else:
+            previous_child = self.contents[position - 1]
+            new_child.previous_sibling = previous_child
+            new_child.previous_sibling.next_sibling = new_child
+            new_child.previous_element = previous_child._last_descendant(False)
+        if new_child.previous_element is not None:
+            new_child.previous_element.next_element = new_child
+
+        new_childs_last_element = new_child._last_descendant(False)
+
+        if position >= len(self.contents):
+            new_child.next_sibling = None
+
+            parent = self
+            parents_next_sibling = None
+            while parents_next_sibling is None and parent is not None:
+                parents_next_sibling = parent.next_sibling
+                parent = parent.parent
+                if parents_next_sibling is not None:
+                    # We found the element that comes next in the document.
+                    break
+            if parents_next_sibling is not None:
+                new_childs_last_element.next_element = parents_next_sibling
+            else:
+                # The last element of this tag is the last element in
+                # the document.
+                new_childs_last_element.next_element = None
+        else:
+            next_child = self.contents[position]
+            new_child.next_sibling = next_child
+            if new_child.next_sibling is not None:
+                new_child.next_sibling.previous_sibling = new_child
+            new_childs_last_element.next_element = next_child
+
+        if new_childs_last_element.next_element is not None:
+            new_childs_last_element.next_element.previous_element = new_childs_last_element
+        self.contents.insert(position, new_child)
+
+    def append(self, tag):
+        """Appends the given tag to the contents of this tag."""
+        self.insert(len(self.contents), tag)
+
+    def extend(self, tags):
+        """Appends the given tags to the contents of this tag."""
+        for tag in tags:
+            self.append(tag)
+
+    def insert_before(self, *args):
+        """Makes the given element(s) the immediate predecessor of this one.
+
+        The elements will have the same parent, and the given elements
+        will be immediately before this one.
+        """
+        parent = self.parent
+        if parent is None:
+            raise ValueError(
+                "Element has no parent, so 'before' has no meaning.")
+        if any(x is self for x in args):
+                raise ValueError("Can't insert an element before itself.")
+        for predecessor in args:
+            # Extract first so that the index won't be screwed up if they
+            # are siblings.
+            if isinstance(predecessor, PageElement):
+                predecessor.extract()
+            index = parent.index(self)
+            parent.insert(index, predecessor)
+
+    def insert_after(self, *args):
+        """Makes the given element(s) the immediate successor of this one.
+
+        The elements will have the same parent, and the given elements
+        will be immediately after this one.
+        """
+        # Do all error checking before modifying the tree.
+        parent = self.parent
+        if parent is None:
+            raise ValueError(
+                "Element has no parent, so 'after' has no meaning.")
+        if any(x is self for x in args):
+            raise ValueError("Can't insert an element after itself.")
+        
+        offset = 0
+        for successor in args:
+            # Extract first so that the index won't be screwed up if they
+            # are siblings.
+            if isinstance(successor, PageElement):
+                successor.extract()
+            index = parent.index(self)
+            parent.insert(index+1+offset, successor)
+            offset += 1
+
+    def find_next(self, name=None, attrs={}, text=None, **kwargs):
+        """Returns the first item that matches the given criteria and
+        appears after this Tag in the document."""
+        return self._find_one(self.find_all_next, name, attrs, text, **kwargs)
+    findNext = find_next  # BS3
+
+    def find_all_next(self, name=None, attrs={}, text=None, limit=None,
+                    **kwargs):
+        """Returns all items that match the given criteria and appear
+        after this Tag in the document."""
+        return self._find_all(name, attrs, text, limit, self.next_elements,
+                             **kwargs)
+    findAllNext = find_all_next  # BS3
+
+    def find_next_sibling(self, name=None, attrs={}, text=None, **kwargs):
+        """Returns the closest sibling to this Tag that matches the
+        given criteria and appears after this Tag in the document."""
+        return self._find_one(self.find_next_siblings, name, attrs, text,
+                             **kwargs)
+    findNextSibling = find_next_sibling  # BS3
+
+    def find_next_siblings(self, name=None, attrs={}, text=None, limit=None,
+                           **kwargs):
+        """Returns the siblings of this Tag that match the given
+        criteria and appear after this Tag in the document."""
+        return self._find_all(name, attrs, text, limit,
+                              self.next_siblings, **kwargs)
+    findNextSiblings = find_next_siblings   # BS3
+    fetchNextSiblings = find_next_siblings  # BS2
+
+    def find_previous(self, name=None, attrs={}, text=None, **kwargs):
+        """Returns the first item that matches the given criteria and
+        appears before this Tag in the document."""
+        return self._find_one(
+            self.find_all_previous, name, attrs, text, **kwargs)
+    findPrevious = find_previous  # BS3
+
+    def find_all_previous(self, name=None, attrs={}, text=None, limit=None,
+                        **kwargs):
+        """Returns all items that match the given criteria and appear
+        before this Tag in the document."""
+        return self._find_all(name, attrs, text, limit, self.previous_elements,
+                           **kwargs)
+    findAllPrevious = find_all_previous  # BS3
+    fetchPrevious = find_all_previous    # BS2
+
+    def find_previous_sibling(self, name=None, attrs={}, text=None, **kwargs):
+        """Returns the closest sibling to this Tag that matches the
+        given criteria and appears before this Tag in the document."""
+        return self._find_one(self.find_previous_siblings, name, attrs, text,
+                             **kwargs)
+    findPreviousSibling = find_previous_sibling  # BS3
+
+    def find_previous_siblings(self, name=None, attrs={}, text=None,
+                               limit=None, **kwargs):
+        """Returns the siblings of this Tag that match the given
+        criteria and appear before this Tag in the document."""
+        return self._find_all(name, attrs, text, limit,
+                              self.previous_siblings, **kwargs)
+    findPreviousSiblings = find_previous_siblings   # BS3
+    fetchPreviousSiblings = find_previous_siblings  # BS2
+
+    def find_parent(self, name=None, attrs={}, **kwargs):
+        """Returns the closest parent of this Tag that matches the given
+        criteria."""
+        # NOTE: We can't use _find_one because findParents takes a different
+        # set of arguments.
+        r = None
+        l = self.find_parents(name, attrs, 1, **kwargs)
+        if l:
+            r = l[0]
+        return r
+    findParent = find_parent  # BS3
+
+    def find_parents(self, name=None, attrs={}, limit=None, **kwargs):
+        """Returns the parents of this Tag that match the given
+        criteria."""
+
+        return self._find_all(name, attrs, None, limit, self.parents,
+                             **kwargs)
+    findParents = find_parents   # BS3
+    fetchParents = find_parents  # BS2
+
+    @property
+    def next(self):
+        return self.next_element
+
+    @property
+    def previous(self):
+        return self.previous_element
+
+    #These methods do the real heavy lifting.
+
+    def _find_one(self, method, name, attrs, text, **kwargs):
+        r = None
+        l = method(name, attrs, text, 1, **kwargs)
+        if l:
+            r = l[0]
+        return r
+
+    def _find_all(self, name, attrs, text, limit, generator, **kwargs):
+        "Iterates over a generator looking for things that match."
+
+        if text is None and 'string' in kwargs:
+            text = kwargs['string']
+            del kwargs['string']
+
+        if isinstance(name, SoupStrainer):
+            strainer = name
+        else:
+            strainer = SoupStrainer(name, attrs, text, **kwargs)
+
+        if text is None and not limit and not attrs and not kwargs:
+            if name is True or name is None:
+                # Optimization to find all tags.
+                result = (element for element in generator
+                          if isinstance(element, Tag))
+                return ResultSet(strainer, result)
+            elif isinstance(name, str):
+                # Optimization to find all tags with a given name.
+                if name.count(':') == 1:
+                    # This is a name with a prefix. If this is a namespace-aware document,
+                    # we need to match the local name against tag.name. If not,
+                    # we need to match the fully-qualified name against tag.name.
+                    prefix, local_name = name.split(':', 1)
+                else:
+                    prefix = None
+                    local_name = name
+                result = (element for element in generator
+                          if isinstance(element, Tag)
+                          and (
+                              element.name == name
+                          ) or (
+                              element.name == local_name
+                              and (prefix is None or element.prefix == prefix)
+                          )
+                )
+                return ResultSet(strainer, result)
+        results = ResultSet(strainer)
+        while True:
+            try:
+                i = next(generator)
+            except StopIteration:
+                break
+            if i:
+                found = strainer.search(i)
+                if found:
+                    results.append(found)
+                    if limit and len(results) >= limit:
+                        break
+        return results
+
+    #These generators can be used to navigate starting from both
+    #NavigableStrings and Tags.
+    @property
+    def next_elements(self):
+        i = self.next_element
+        while i is not None:
+            yield i
+            i = i.next_element
+
+    @property
+    def next_siblings(self):
+        i = self.next_sibling
+        while i is not None:
+            yield i
+            i = i.next_sibling
+
+    @property
+    def previous_elements(self):
+        i = self.previous_element
+        while i is not None:
+            yield i
+            i = i.previous_element
+
+    @property
+    def previous_siblings(self):
+        i = self.previous_sibling
+        while i is not None:
+            yield i
+            i = i.previous_sibling
+
+    @property
+    def parents(self):
+        i = self.parent
+        while i is not None:
+            yield i
+            i = i.parent
+
+    # Old non-property versions of the generators, for backwards
+    # compatibility with BS3.
+    def nextGenerator(self):
+        return self.next_elements
+
+    def nextSiblingGenerator(self):
+        return self.next_siblings
+
+    def previousGenerator(self):
+        return self.previous_elements
+
+    def previousSiblingGenerator(self):
+        return self.previous_siblings
+
+    def parentGenerator(self):
+        return self.parents
+
+
+class NavigableString(str, PageElement):
+
+    PREFIX = ''
+    SUFFIX = ''
+
+    # We can't tell just by looking at a string whether it's contained
+    # in an XML document or an HTML document.
+
+    known_xml = None
+
+    def __new__(cls, value):
+        """Create a new NavigableString.
+
+        When unpickling a NavigableString, this method is called with
+        the string in DEFAULT_OUTPUT_ENCODING. That encoding needs to be
+        passed in to the superclass's __new__ or the superclass won't know
+        how to handle non-ASCII characters.
+        """
+        if isinstance(value, str):
+            u = str.__new__(cls, value)
+        else:
+            u = str.__new__(cls, value, DEFAULT_OUTPUT_ENCODING)
+        u.setup()
+        return u
+
+    def __copy__(self):
+        """A copy of a NavigableString has the same contents and class
+        as the original, but it is not connected to the parse tree.
+        """
+        return type(self)(self)
+
+    def __getnewargs__(self):
+        return (str(self),)
+
+    def __getattr__(self, attr):
+        """text.string gives you text. This is for backwards
+        compatibility for Navigable*String, but for CData* it lets you
+        get the string without the CData wrapper."""
+        if attr == 'string':
+            return self
+        else:
+            raise AttributeError(
+                "'%s' object has no attribute '%s'" % (
+                    self.__class__.__name__, attr))
+
+    def output_ready(self, formatter="minimal"):
+        """Run the string through the provided formatter."""
+        output = self.format_string(self, formatter)
+        return self.PREFIX + output + self.SUFFIX
+
+    @property
+    def name(self):
+        return None
+
+    @name.setter
+    def name(self, name):
+        raise AttributeError("A NavigableString cannot be given a name.")
+
+class PreformattedString(NavigableString):
+    """A NavigableString not subject to the normal formatting rules.
+
+    The string will be passed into the formatter (to trigger side effects),
+    but the return value will be ignored.
+    """
+
+    def output_ready(self, formatter=None):
+        """CData strings are passed into the formatter, purely
+        for any side effects. The return value is ignored.
+        """
+        if formatter is not None:
+            ignore = self.format_string(self, formatter)
+        return self.PREFIX + self + self.SUFFIX
+
+class CData(PreformattedString):
+
+    PREFIX = '<![CDATA['
+    SUFFIX = ']]>'
+
+class ProcessingInstruction(PreformattedString):
+    """A SGML processing instruction."""
+
+    PREFIX = '<?'
+    SUFFIX = '>'
+
+class XMLProcessingInstruction(ProcessingInstruction):
+    """An XML processing instruction."""
+    PREFIX = '<?'
+    SUFFIX = '?>'
+
+class Comment(PreformattedString):
+
+    PREFIX = '<!--'
+    SUFFIX = '-->'
+
+
+class Declaration(PreformattedString):
+    PREFIX = '<?'
+    SUFFIX = '?>'
+
+
+class Doctype(PreformattedString):
+
+    @classmethod
+    def for_name_and_ids(cls, name, pub_id, system_id):
+        value = name or ''
+        if pub_id is not None:
+            value += ' PUBLIC "%s"' % pub_id
+            if system_id is not None:
+                value += ' "%s"' % system_id
+        elif system_id is not None:
+            value += ' SYSTEM "%s"' % system_id
+
+        return Doctype(value)
+
+    PREFIX = '<!DOCTYPE '
+    SUFFIX = '>\n'
+
+
+class Tag(PageElement):
+
+    """Represents a found HTML tag with its attributes and contents."""
+
+    def __init__(self, parser=None, builder=None, name=None, namespace=None,
+                 prefix=None, attrs=None, parent=None, previous=None,
+                 is_xml=None):
+        "Basic constructor."
+
+        if parser is None:
+            self.parser_class = None
+        else:
+            # We don't actually store the parser object: that lets extracted
+            # chunks be garbage-collected.
+            self.parser_class = parser.__class__
+        if name is None:
+            raise ValueError("No value provided for new tag's name.")
+        self.name = name
+        self.namespace = namespace
+        self.prefix = prefix
+        if attrs is None:
+            attrs = {}
+        elif attrs:
+            if builder is not None and builder.cdata_list_attributes:
+                attrs = builder._replace_cdata_list_attribute_values(
+                    self.name, attrs)
+            else:
+                attrs = dict(attrs)
+        else:
+            attrs = dict(attrs)
+
+        # If possible, determine ahead of time whether this tag is an
+        # XML tag.
+        if builder:
+            self.known_xml = builder.is_xml
+        else:
+            self.known_xml = is_xml
+        self.attrs = attrs
+        self.contents = []
+        self.setup(parent, previous)
+        self.hidden = False
+
+        if builder is None:
+            # In the absence of a TreeBuilder, assume this tag is nothing
+            # special.
+            self.can_be_empty_element = False
+            self.cdata_list_attributes = None
+        else:
+            # Set up any substitutions for this tag, such as the charset in a META tag.
+            builder.set_up_substitutions(self)
+
+            # Ask the TreeBuilder whether this tag might be an empty-element tag.
+            self.can_be_empty_element = builder.can_be_empty_element(name)
+
+            # Keep track of the list of attributes of this tag that
+            # might need to be treated as a list.
+            #
+            # For performance reasons, we store the whole data structure
+            # rather than asking the question of every tag. Asking would
+            # require building a new data structure every time, and
+            # (unlike can_be_empty_element), we almost never need
+            # to check this.
+            self.cdata_list_attributes = builder.cdata_list_attributes
+
+            # Keep track of the names that might cause this tag to be treated as a
+            # whitespace-preserved tag.
+            self.preserve_whitespace_tags = builder.preserve_whitespace_tags
+            
+    parserClass = _alias("parser_class")  # BS3
+
+    def __copy__(self):
+        """A copy of a Tag is a new Tag, unconnected to the parse tree.
+        Its contents are a copy of the old Tag's contents.
+        """
+        clone = type(self)(None, self.builder, self.name, self.namespace,
+                           self.prefix, self.attrs, is_xml=self._is_xml)
+        for attr in ('can_be_empty_element', 'hidden'):
+            setattr(clone, attr, getattr(self, attr))
+        for child in self.contents:
+            clone.append(child.__copy__())
+        return clone
+
+    @property
+    def is_empty_element(self):
+        """Is this tag an empty-element tag? (aka a self-closing tag)
+
+        A tag that has contents is never an empty-element tag.
+
+        A tag that has no contents may or may not be an empty-element
+        tag. It depends on the builder used to create the tag. If the
+        builder has a designated list of empty-element tags, then only
+        a tag whose name shows up in that list is considered an
+        empty-element tag.
+
+        If the builder has no designated list of empty-element tags,
+        then any tag with no contents is an empty-element tag.
+        """
+        return len(self.contents) == 0 and self.can_be_empty_element
+    isSelfClosing = is_empty_element  # BS3
+
+    @property
+    def string(self):
+        """Convenience property to get the single string within this tag.
+
+        :Return: If this tag has a single string child, return value
+         is that string. If this tag has no children, or more than one
+         child, return value is None. If this tag has one child tag,
+         return value is the 'string' attribute of the child tag,
+         recursively.
+        """
+        if len(self.contents) != 1:
+            return None
+        child = self.contents[0]
+        if isinstance(child, NavigableString):
+            return child
+        return child.string
+
+    @string.setter
+    def string(self, string):
+        self.clear()
+        self.append(string.__class__(string))
+
+    def _all_strings(self, strip=False, types=(NavigableString, CData)):
+        """Yield all strings of certain classes, possibly stripping them.
+
+        By default, yields only NavigableString and CData objects. So
+        no comments, processing instructions, etc.
+        """
+        for descendant in self.descendants:
+            if (
+                (types is None and not isinstance(descendant, NavigableString))
+                or
+                (types is not None and type(descendant) not in types)):
+                continue
+            if strip:
+                descendant = descendant.strip()
+                if len(descendant) == 0:
+                    continue
+            yield descendant
+
+    strings = property(_all_strings)
+
+    @property
+    def stripped_strings(self):
+        for string in self._all_strings(True):
+            yield string
+
+    def get_text(self, separator="", strip=False,
+                 types=(NavigableString, CData)):
+        """
+        Get all child strings, concatenated using the given separator.
+        """
+        return separator.join([s for s in self._all_strings(
+                    strip, types=types)])
+    getText = get_text
+    text = property(get_text)
+
+    def decompose(self):
+        """Recursively destroys the contents of this tree."""
+        self.extract()
+        i = self
+        while i is not None:
+            next = i.next_element
+            i.__dict__.clear()
+            i.contents = []
+            i = next
+
+    def clear(self, decompose=False):
+        """
+        Extract all children. If decompose is True, decompose instead.
+        """
+        if decompose:
+            for element in self.contents[:]:
+                if isinstance(element, Tag):
+                    element.decompose()
+                else:
+                    element.extract()
+        else:
+            for element in self.contents[:]:
+                element.extract()
+
+    def smooth(self):
+        """Smooth out this element's children by consolidating consecutive strings.
+
+        This makes pretty-printed output look more natural following a
+        lot of operations that modified the tree.
+        """
+        # Mark the first position of every pair of children that need
+        # to be consolidated.  Do this rather than making a copy of
+        # self.contents, since in most cases very few strings will be
+        # affected.
+        marked = []
+        for i, a in enumerate(self.contents):
+            if isinstance(a, Tag):
+                # Recursively smooth children.
+                a.smooth()
+            if i == len(self.contents)-1:
+                # This is the last item in .contents, and it's not a
+                # tag. There's no chance it needs any work.
+                continue
+            b = self.contents[i+1]
+            if (isinstance(a, NavigableString)
+                and isinstance(b, NavigableString)
+                and not isinstance(a, PreformattedString)
+                and not isinstance(b, PreformattedString)
+            ):
+                marked.append(i)
+
+        # Go over the marked positions in reverse order, so that
+        # removing items from .contents won't affect the remaining
+        # positions.
+        for i in reversed(marked):
+            a = self.contents[i]
+            b = self.contents[i+1]
+            b.extract()
+            n = NavigableString(a+b)
+            a.replace_with(n)
+
+    def index(self, element):
+        """
+        Find the index of a child by identity, not value. Avoids issues with
+        tag.contents.index(element) getting the index of equal elements.
+        """
+        for i, child in enumerate(self.contents):
+            if child is element:
+                return i
+        raise ValueError("Tag.index: element not in tag")
+
+    def get(self, key, default=None):
+        """Returns the value of the 'key' attribute for the tag, or
+        the value given for 'default' if it doesn't have that
+        attribute."""
+        return self.attrs.get(key, default)
+
+    def get_attribute_list(self, key, default=None):
+        """The same as get(), but always returns a list."""
+        value = self.get(key, default)
+        if not isinstance(value, list):
+            value = [value]
+        return value
+    
+    def has_attr(self, key):
+        return key in self.attrs
+
+    def __hash__(self):
+        return str(self).__hash__()
+
+    def __getitem__(self, key):
+        """tag[key] returns the value of the 'key' attribute for the tag,
+        and throws an exception if it's not there."""
+        return self.attrs[key]
+
+    def __iter__(self):
+        "Iterating over a tag iterates over its contents."
+        return iter(self.contents)
+
+    def __len__(self):
+        "The length of a tag is the length of its list of contents."
+        return len(self.contents)
+
+    def __contains__(self, x):
+        return x in self.contents
+
+    def __bool__(self):
+        "A tag is non-None even if it has no contents."
+        return True
+
+    def __setitem__(self, key, value):
+        """Setting tag[key] sets the value of the 'key' attribute for the
+        tag."""
+        self.attrs[key] = value
+
+    def __delitem__(self, key):
+        "Deleting tag[key] deletes all 'key' attributes for the tag."
+        self.attrs.pop(key, None)
+
+    def __call__(self, *args, **kwargs):
+        """Calling a tag like a function is the same as calling its
+        find_all() method. Eg. tag('a') returns a list of all the A tags
+        found within this tag."""
+        return self.find_all(*args, **kwargs)
+
+    def __getattr__(self, tag):
+        #print "Getattr %s.%s" % (self.__class__, tag)
+        if len(tag) > 3 and tag.endswith('Tag'):
+            # BS3: soup.aTag -> "soup.find("a")
+            tag_name = tag[:-3]
+            warnings.warn(
+                '.%(name)sTag is deprecated, use .find("%(name)s") instead. If you really were looking for a tag called %(name)sTag, use .find("%(name)sTag")' % dict(
+                    name=tag_name
+                )
+            )
+            return self.find(tag_name)
+        # We special case contents to avoid recursion.
+        elif not tag.startswith("__") and not tag == "contents":
+            return self.find(tag)
+        raise AttributeError(
+            "'%s' object has no attribute '%s'" % (self.__class__, tag))
+
+    def __eq__(self, other):
+        """Returns true iff this tag has the same name, the same attributes,
+        and the same contents (recursively) as the given tag."""
+        if self is other:
+            return True
+        if (not hasattr(other, 'name') or
+            not hasattr(other, 'attrs') or
+            not hasattr(other, 'contents') or
+            self.name != other.name or
+            self.attrs != other.attrs or
+            len(self) != len(other)):
+            return False
+        for i, my_child in enumerate(self.contents):
+            if my_child != other.contents[i]:
+                return False
+        return True
+
+    def __ne__(self, other):
+        """Returns true iff this tag is not identical to the other tag,
+        as defined in __eq__."""
+        return not self == other
+
+    def __repr__(self, encoding="unicode-escape"):
+        """Renders this tag as a string."""
+        if PY3K:
+            # "The return value must be a string object", i.e. Unicode
+            return self.decode()
+        else:
+            # "The return value must be a string object", i.e. a bytestring.
+            # By convention, the return value of __repr__ should also be
+            # an ASCII string.
+            return self.encode(encoding)
+
+    def __unicode__(self):
+        return self.decode()
+
+    def __str__(self):
+        if PY3K:
+            return self.decode()
+        else:
+            return self.encode()
+
+    if PY3K:
+        __str__ = __repr__ = __unicode__
+
+    def encode(self, encoding=DEFAULT_OUTPUT_ENCODING,
+               indent_level=None, formatter="minimal",
+               errors="xmlcharrefreplace"):
+        # Turn the data structure into Unicode, then encode the
+        # Unicode.
+        u = self.decode(indent_level, encoding, formatter)
+        return u.encode(encoding, errors)
+
+    def decode(self, indent_level=None,
+               eventual_encoding=DEFAULT_OUTPUT_ENCODING,
+               formatter="minimal"):
+        """Returns a Unicode representation of this tag and its contents.
+
+        :param eventual_encoding: The tag is destined to be
+           encoded into this encoding. This method is _not_
+           responsible for performing that encoding. This information
+           is passed in so that it can be substituted in if the
+           document contains a <META> tag that mentions the document's
+           encoding.
+        """
+
+        # First off, turn a non-Formatter `formatter` into a Formatter
+        # object. This will stop the lookup from happening over and
+        # over again.
+        if not isinstance(formatter, Formatter):
+            formatter = self.formatter_for_name(formatter)
+        attributes = formatter.attributes(self)
+        attrs = []
+        for key, val in attributes:
+            if val is None:
+                decoded = key
+            else:
+                if isinstance(val, list) or isinstance(val, tuple):
+                    val = ' '.join(val)
+                elif not isinstance(val, str):
+                    val = str(val)
+                elif (
+                        isinstance(val, AttributeValueWithCharsetSubstitution)
+                        and eventual_encoding is not None
+                ):
+                    val = val.encode(eventual_encoding)
+
+                text = formatter.attribute_value(val)
+                decoded = (
+                    str(key) + '='
+                    + formatter.quoted_attribute_value(text))
+            attrs.append(decoded)
+        close = ''
+        closeTag = ''
+
+        prefix = ''
+        if self.prefix:
+            prefix = self.prefix + ":"
+
+        if self.is_empty_element:
+            close = formatter.void_element_close_prefix or ''
+        else:
+            closeTag = '</%s%s>' % (prefix, self.name)
+
+        pretty_print = self._should_pretty_print(indent_level)
+        space = ''
+        indent_space = ''
+        if indent_level is not None:
+            indent_space = (' ' * (indent_level - 1))
+        if pretty_print:
+            space = indent_space
+            indent_contents = indent_level + 1
+        else:
+            indent_contents = None
+        contents = self.decode_contents(
+            indent_contents, eventual_encoding, formatter
+        )
+
+        if self.hidden:
+            # This is the 'document root' object.
+            s = contents
+        else:
+            s = []
+            attribute_string = ''
+            if attrs:
+                attribute_string = ' ' + ' '.join(attrs)
+            if indent_level is not None:
+                # Even if this particular tag is not pretty-printed,
+                # we should indent up to the start of the tag.
+                s.append(indent_space)
+            s.append('<%s%s%s%s>' % (
+                    prefix, self.name, attribute_string, close))
+            if pretty_print:
+                s.append("\n")
+            s.append(contents)
+            if pretty_print and contents and contents[-1] != "\n":
+                s.append("\n")
+            if pretty_print and closeTag:
+                s.append(space)
+            s.append(closeTag)
+            if indent_level is not None and closeTag and self.next_sibling:
+                # Even if this particular tag is not pretty-printed,
+                # we're now done with the tag, and we should add a
+                # newline if appropriate.
+                s.append("\n")
+            s = ''.join(s)
+        return s
+
+    def _should_pretty_print(self, indent_level):
+        """Should this tag be pretty-printed?"""
+        return (
+            indent_level is not None
+            and self.name not in self.preserve_whitespace_tags
+        )
+
+    def prettify(self, encoding=None, formatter="minimal"):
+        if encoding is None:
+            return self.decode(True, formatter=formatter)
+        else:
+            return self.encode(encoding, True, formatter=formatter)
+
+    def decode_contents(self, indent_level=None,
+                       eventual_encoding=DEFAULT_OUTPUT_ENCODING,
+                       formatter="minimal"):
+        """Renders the contents of this tag as a Unicode string.
+
+        :param indent_level: Each line of the rendering will be
+           indented this many spaces.
+
+        :param eventual_encoding: The tag is destined to be
+           encoded into this encoding. decode_contents() is _not_
+           responsible for performing that encoding. This information
+           is passed in so that it can be substituted in if the
+           document contains a <META> tag that mentions the document's
+           encoding.
+
+        :param formatter: A Formatter object, or a string naming one of
+            the standard Formatters.
+        """
+        # First off, turn a string formatter into a Formatter object. This
+        # will stop the lookup from happening over and over again.
+        if not isinstance(formatter, Formatter):
+            formatter = self.formatter_for_name(formatter)
+
+        pretty_print = (indent_level is not None)
+        s = []
+        for c in self:
+            text = None
+            if isinstance(c, NavigableString):
+                text = c.output_ready(formatter)
+            elif isinstance(c, Tag):
+                s.append(c.decode(indent_level, eventual_encoding,
+                                  formatter))
+            preserve_whitespace = (
+                self.preserve_whitespace_tags and self.name in self.preserve_whitespace_tags
+            )
+            if text and indent_level and not preserve_whitespace:
+                text = text.strip()
+            if text:
+                if pretty_print and not preserve_whitespace:
+                    s.append(" " * (indent_level - 1))
+                s.append(text)
+                if pretty_print and not preserve_whitespace:
+                    s.append("\n")
+        return ''.join(s)
+       
+    def encode_contents(
+        self, indent_level=None, encoding=DEFAULT_OUTPUT_ENCODING,
+        formatter="minimal"):
+        """Renders the contents of this tag as a bytestring.
+
+        :param indent_level: Each line of the rendering will be
+           indented this many spaces.
+
+        :param eventual_encoding: The bytestring will be in this encoding.
+
+        :param formatter: The output formatter responsible for converting
+           entities to Unicode characters.
+        """
+
+        contents = self.decode_contents(indent_level, encoding, formatter)
+        return contents.encode(encoding)
+
+    # Old method for BS3 compatibility
+    def renderContents(self, encoding=DEFAULT_OUTPUT_ENCODING,
+                       prettyPrint=False, indentLevel=0):
+        if not prettyPrint:
+            indentLevel = None
+        return self.encode_contents(
+            indent_level=indentLevel, encoding=encoding)
+
+    #Soup methods
+
+    def find(self, name=None, attrs={}, recursive=True, text=None,
+             **kwargs):
+        """Return only the first child of this Tag matching the given
+        criteria."""
+        r = None
+        l = self.find_all(name, attrs, recursive, text, 1, **kwargs)
+        if l:
+            r = l[0]
+        return r
+    findChild = find
+
+    def find_all(self, name=None, attrs={}, recursive=True, text=None,
+                 limit=None, **kwargs):
+        """Extracts a list of Tag objects that match the given
+        criteria.  You can specify the name of the Tag and any
+        attributes you want the Tag to have.
+
+        The value of a key-value pair in the 'attrs' map can be a
+        string, a list of strings, a regular expression object, or a
+        callable that takes a string and returns whether or not the
+        string matches for some custom definition of 'matches'. The
+        same is true of the tag name."""
+
+        generator = self.descendants
+        if not recursive:
+            generator = self.children
+        return self._find_all(name, attrs, text, limit, generator, **kwargs)
+    findAll = find_all       # BS3
+    findChildren = find_all  # BS2
+
+    #Generator methods
+    @property
+    def children(self):
+        # return iter() to make the purpose of the method clear
+        return iter(self.contents)  # XXX This seems to be untested.
+
+    @property
+    def descendants(self):
+        if not len(self.contents):
+            return
+        stopNode = self._last_descendant().next_element
+        current = self.contents[0]
+        while current is not stopNode:
+            yield current
+            current = current.next_element
+
+    # CSS selector code
+    def select_one(self, selector, namespaces=None, **kwargs):
+        """Perform a CSS selection operation on the current element."""
+        value = self.select(selector, namespaces, 1, **kwargs)
+        if value:
+            return value[0]
+        return None
+
+    def select(self, selector, namespaces=None, limit=None, **kwargs):
+        """Perform a CSS selection operation on the current element.
+
+        This uses the SoupSieve library.
+
+        :param selector: A string containing a CSS selector.
+
+        :param namespaces: A dictionary mapping namespace prefixes
+        used in the CSS selector to namespace URIs. By default,
+        Beautiful Soup will use the prefixes it encountered while
+        parsing the document.
+
+        :param limit: After finding this number of results, stop looking.
+
+        :param kwargs: Any extra arguments you'd like to pass in to
+        soupsieve.select().
+        """
+        if namespaces is None:
+            namespaces = self._namespaces
+        
+        if limit is None:
+            limit = 0
+        if soupsieve is None:
+            raise NotImplementedError(
+                "Cannot execute CSS selectors because the soupsieve package is not installed."
+            )
+            
+        return soupsieve.select(selector, self, namespaces, limit, **kwargs)
+
+    # Old names for backwards compatibility
+    def childGenerator(self):
+        return self.children
+
+    def recursiveChildGenerator(self):
+        return self.descendants
+
+    def has_key(self, key):
+        """This was kind of misleading because has_key() (attributes)
+        was different from __in__ (contents). has_key() is gone in
+        Python 3, anyway."""
+        warnings.warn('has_key is deprecated. Use has_attr("%s") instead.' % (
+                key))
+        return self.has_attr(key)
+
+# Next, a couple classes to represent queries and their results.
+class SoupStrainer(object):
+    """Encapsulates a number of ways of matching a markup element (tag or
+    text)."""
+
+    def __init__(self, name=None, attrs={}, text=None, **kwargs):
+        self.name = self._normalize_search_value(name)
+        if not isinstance(attrs, dict):
+            # Treat a non-dict value for attrs as a search for the 'class'
+            # attribute.
+            kwargs['class'] = attrs
+            attrs = None
+
+        if 'class_' in kwargs:
+            # Treat class_="foo" as a search for the 'class'
+            # attribute, overriding any non-dict value for attrs.
+            kwargs['class'] = kwargs['class_']
+            del kwargs['class_']
+
+        if kwargs:
+            if attrs:
+                attrs = attrs.copy()
+                attrs.update(kwargs)
+            else:
+                attrs = kwargs
+        normalized_attrs = {}
+        for key, value in list(attrs.items()):
+            normalized_attrs[key] = self._normalize_search_value(value)
+
+        self.attrs = normalized_attrs
+        self.text = self._normalize_search_value(text)
+
+    def _normalize_search_value(self, value):
+        # Leave it alone if it's a Unicode string, a callable, a
+        # regular expression, a boolean, or None.
+        if (isinstance(value, str) or isinstance(value, Callable) or hasattr(value, 'match')
+            or isinstance(value, bool) or value is None):
+            return value
+
+        # If it's a bytestring, convert it to Unicode, treating it as UTF-8.
+        if isinstance(value, bytes):
+            return value.decode("utf8")
+
+        # If it's listlike, convert it into a list of strings.
+        if hasattr(value, '__iter__'):
+            new_value = []
+            for v in value:
+                if (hasattr(v, '__iter__') and not isinstance(v, bytes)
+                    and not isinstance(v, str)):
+                    # This is almost certainly the user's mistake. In the
+                    # interests of avoiding infinite loops, we'll let
+                    # it through as-is rather than doing a recursive call.
+                    new_value.append(v)
+                else:
+                    new_value.append(self._normalize_search_value(v))
+            return new_value
+
+        # Otherwise, convert it into a Unicode string.
+        # The unicode(str()) thing is so this will do the same thing on Python 2
+        # and Python 3.
+        return str(str(value))
+
+    def __str__(self):
+        if self.text:
+            return self.text
+        else:
+            return "%s|%s" % (self.name, self.attrs)
+
+    def search_tag(self, markup_name=None, markup_attrs={}):
+        found = None
+        markup = None
+        if isinstance(markup_name, Tag):
+            markup = markup_name
+            markup_attrs = markup
+        call_function_with_tag_data = (
+            isinstance(self.name, Callable)
+            and not isinstance(markup_name, Tag))
+
+        if ((not self.name)
+            or call_function_with_tag_data
+            or (markup and self._matches(markup, self.name))
+            or (not markup and self._matches(markup_name, self.name))):
+            if call_function_with_tag_data:
+                match = self.name(markup_name, markup_attrs)
+            else:
+                match = True
+                markup_attr_map = None
+                for attr, match_against in list(self.attrs.items()):
+                    if not markup_attr_map:
+                        if hasattr(markup_attrs, 'get'):
+                            markup_attr_map = markup_attrs
+                        else:
+                            markup_attr_map = {}
+                            for k, v in markup_attrs:
+                                markup_attr_map[k] = v
+                    attr_value = markup_attr_map.get(attr)
+                    if not self._matches(attr_value, match_against):
+                        match = False
+                        break
+            if match:
+                if markup:
+                    found = markup
+                else:
+                    found = markup_name
+        if found and self.text and not self._matches(found.string, self.text):
+            found = None
+        return found
+    searchTag = search_tag
+
+    def search(self, markup):
+        # print 'looking for %s in %s' % (self, markup)
+        found = None
+        # If given a list of items, scan it for a text element that
+        # matches.
+        if hasattr(markup, '__iter__') and not isinstance(markup, (Tag, str)):
+            for element in markup:
+                if isinstance(element, NavigableString) \
+                       and self.search(element):
+                    found = element
+                    break
+        # If it's a Tag, make sure its name or attributes match.
+        # Don't bother with Tags if we're searching for text.
+        elif isinstance(markup, Tag):
+            if not self.text or self.name or self.attrs:
+                found = self.search_tag(markup)
+        # If it's text, make sure the text matches.
+        elif isinstance(markup, NavigableString) or \
+                 isinstance(markup, str):
+            if not self.name and not self.attrs and self._matches(markup, self.text):
+                found = markup
+        else:
+            raise Exception(
+                "I don't know how to match against a %s" % markup.__class__)
+        return found
+
+    def _matches(self, markup, match_against, already_tried=None):
+        # print u"Matching %s against %s" % (markup, match_against)
+        result = False
+        if isinstance(markup, list) or isinstance(markup, tuple):
+            # This should only happen when searching a multi-valued attribute
+            # like 'class'.
+            for item in markup:
+                if self._matches(item, match_against):
+                    return True
+            # We didn't match any particular value of the multivalue
+            # attribute, but maybe we match the attribute value when
+            # considered as a string.
+            if self._matches(' '.join(markup), match_against):
+                return True
+            return False
+        
+        if match_against is True:
+            # True matches any non-None value.
+            return markup is not None
+
+        if isinstance(match_against, Callable):
+            return match_against(markup)
+
+        # Custom callables take the tag as an argument, but all
+        # other ways of matching match the tag name as a string.
+        original_markup = markup
+        if isinstance(markup, Tag):
+            markup = markup.name
+
+        # Ensure that `markup` is either a Unicode string, or None.
+        markup = self._normalize_search_value(markup)
+
+        if markup is None:
+            # None matches None, False, an empty string, an empty list, and so on.
+            return not match_against
+
+        if (hasattr(match_against, '__iter__')
+            and not isinstance(match_against, str)):
+            # We're asked to match against an iterable of items.
+            # The markup must be match at least one item in the
+            # iterable. We'll try each one in turn.
+            #
+            # To avoid infinite recursion we need to keep track of
+            # items we've already seen.
+            if not already_tried:
+                already_tried = set()
+            for item in match_against:
+                if item.__hash__:
+                    key = item
+                else:
+                    key = id(item)
+                if key in already_tried:
+                    continue
+                else:
+                    already_tried.add(key)
+                    if self._matches(original_markup, item, already_tried):
+                        return True
+            else:
+                return False
+        
+        # Beyond this point we might need to run the test twice: once against
+        # the tag's name and once against its prefixed name.
+        match = False
+        
+        if not match and isinstance(match_against, str):
+            # Exact string match
+            match = markup == match_against
+
+        if not match and hasattr(match_against, 'search'):
+            # Regexp match
+            return match_against.search(markup)
+
+        if (not match
+            and isinstance(original_markup, Tag)
+            and original_markup.prefix):
+            # Try the whole thing again with the prefixed tag name.
+            return self._matches(
+                original_markup.prefix + ':' + original_markup.name, match_against
+            )
+
+        return match
+
+
+class ResultSet(list):
+    """A ResultSet is just a list that keeps track of the SoupStrainer
+    that created it."""
+    def __init__(self, source, result=()):
+        super(ResultSet, self).__init__(result)
+        self.source = source
+
+    def __getattr__(self, key):
+        raise AttributeError(
+            "ResultSet object has no attribute '%s'. You're probably treating a list of items like a single item. Did you call find_all() when you meant to call find()?" % key
+        )
diff --git a/libs/bs4/formatter.py b/libs/bs4/formatter.py
new file mode 100644
index 000000000..7dbaa3850
--- /dev/null
+++ b/libs/bs4/formatter.py
@@ -0,0 +1,99 @@
+from bs4.dammit import EntitySubstitution
+
+class Formatter(EntitySubstitution):
+    """Describes a strategy to use when outputting a parse tree to a string.
+
+    Some parts of this strategy come from the distinction between
+    HTML4, HTML5, and XML. Others are configurable by the user.
+    """
+    # Registries of XML and HTML formatters.
+    XML_FORMATTERS = {}
+    HTML_FORMATTERS = {}
+
+    HTML = 'html'
+    XML = 'xml'
+
+    HTML_DEFAULTS = dict(
+        cdata_containing_tags=set(["script", "style"]),
+    )
+
+    def _default(self, language, value, kwarg):
+        if value is not None:
+            return value
+        if language == self.XML:
+            return set()
+        return self.HTML_DEFAULTS[kwarg]
+
+    def __init__(
+            self, language=None, entity_substitution=None,
+            void_element_close_prefix='/', cdata_containing_tags=None,
+    ):
+        """
+
+        :param void_element_close_prefix: By default, represent void
+        elements as <tag/> rather than <tag>
+        """
+        self.language = language
+        self.entity_substitution = entity_substitution
+        self.void_element_close_prefix = void_element_close_prefix
+        self.cdata_containing_tags = self._default(
+            language, cdata_containing_tags, 'cdata_containing_tags'
+        )
+            
+    def substitute(self, ns):
+        """Process a string that needs to undergo entity substitution."""
+        if not self.entity_substitution:
+            return ns
+        from .element import NavigableString
+        if (isinstance(ns, NavigableString)
+            and ns.parent is not None
+            and ns.parent.name in self.cdata_containing_tags):
+            # Do nothing.
+            return ns
+        # Substitute.
+        return self.entity_substitution(ns)
+
+    def attribute_value(self, value):
+        """Process the value of an attribute."""
+        return self.substitute(value)
+    
+    def attributes(self, tag):
+        """Reorder a tag's attributes however you want."""
+        return sorted(tag.attrs.items())
+
+   
+class HTMLFormatter(Formatter):
+    REGISTRY = {}
+    def __init__(self, *args, **kwargs):
+        return super(HTMLFormatter, self).__init__(self.HTML, *args, **kwargs)
+
+    
+class XMLFormatter(Formatter):
+    REGISTRY = {}
+    def __init__(self, *args, **kwargs):
+        return super(XMLFormatter, self).__init__(self.XML, *args, **kwargs)
+
+
+# Set up aliases for the default formatters.
+HTMLFormatter.REGISTRY['html'] = HTMLFormatter(
+    entity_substitution=EntitySubstitution.substitute_html
+)
+HTMLFormatter.REGISTRY["html5"] = HTMLFormatter(
+    entity_substitution=EntitySubstitution.substitute_html,
+    void_element_close_prefix = None
+)
+HTMLFormatter.REGISTRY["minimal"] = HTMLFormatter(
+    entity_substitution=EntitySubstitution.substitute_xml
+)
+HTMLFormatter.REGISTRY[None] = HTMLFormatter(
+    entity_substitution=None
+)
+XMLFormatter.REGISTRY["html"] =  XMLFormatter(
+    entity_substitution=EntitySubstitution.substitute_html
+)
+XMLFormatter.REGISTRY["minimal"] = XMLFormatter(
+    entity_substitution=EntitySubstitution.substitute_xml
+)
+XMLFormatter.REGISTRY[None] = Formatter(
+    Formatter(Formatter.XML, entity_substitution=None)
+)
diff --git a/libs/bs4/testing.py b/libs/bs4/testing.py
new file mode 100644
index 000000000..cc9966601
--- /dev/null
+++ b/libs/bs4/testing.py
@@ -0,0 +1,992 @@
+# encoding: utf-8
+"""Helper classes for tests."""
+
+# Use of this source code is governed by the MIT license.
+__license__ = "MIT"
+
+import pickle
+import copy
+import functools
+import unittest
+from unittest import TestCase
+from bs4 import BeautifulSoup
+from bs4.element import (
+    CharsetMetaAttributeValue,
+    Comment,
+    ContentMetaAttributeValue,
+    Doctype,
+    SoupStrainer,
+    Tag
+)
+
+from bs4.builder import HTMLParserTreeBuilder
+default_builder = HTMLParserTreeBuilder
+
+BAD_DOCUMENT = """A bare string
+<!DOCTYPE xsl:stylesheet SYSTEM "htmlent.dtd">
+<!DOCTYPE xsl:stylesheet PUBLIC "htmlent.dtd">
+<div><![CDATA[A CDATA section where it doesn't belong]]></div>
+<div><svg><![CDATA[HTML5 does allow CDATA sections in SVG]]></svg></div>
+<div>A <meta> tag</div>
+<div>A <br> tag that supposedly has contents.</br></div>
+<div>AT&T</div>
+<div><textarea>Within a textarea, markup like <b> tags and <&<&amp; should be treated as literal</textarea></div>
+<div><script>if (i < 2) { alert("<b>Markup within script tags should be treated as literal.</b>"); }</script></div>
+<div>This numeric entity is missing the final semicolon: <x t="pi&#241ata"></div>
+<div><a href="http://example.com/</a> that attribute value never got closed</div>
+<div><a href="foo</a>, </a><a href="bar">that attribute value was closed by the subsequent tag</a></div>
+<! This document starts with a bogus declaration ><div>a</div>
+<div>This document contains <!an incomplete declaration <div>(do you see it?)</div>
+<div>This document ends with <!an incomplete declaration
+<div><a style={height:21px;}>That attribute value was bogus</a></div>
+<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">The doctype is invalid because it contains extra whitespace
+<div><table><td nowrap>That boolean attribute had no value</td></table></div>
+<div>Here's a nonexistent entity: &#foo; (do you see it?)</div>
+<div>This document ends before the entity finishes: &gt
+<div><p>Paragraphs shouldn't contain block display elements, but this one does: <dl><dt>you see?</dt></p>
+<b b="20" a="1" b="10" a="2" a="3" a="4">Multiple values for the same attribute.</b>
+<div><table><tr><td>Here's a table</td></tr></table></div>
+<div><table id="1"><tr><td>Here's a nested table:<table id="2"><tr><td>foo</td></tr></table></td></div>
+<div>This tag contains nothing but whitespace: <b>    </b></div>
+<div><blockquote><p><b>This p tag is cut off by</blockquote></p>the end of the blockquote tag</div>
+<div><table><div>This table contains bare markup</div></table></div>
+<div><div id="1">\n <a href="link1">This link is never closed.\n</div>\n<div id="2">\n <div id="3">\n   <a href="link2">This link is closed.</a>\n  </div>\n</div></div>
+<div>This document contains a <!DOCTYPE surprise>surprise doctype</div>
+<div><a><B><Cd><EFG>Mixed case tags are folded to lowercase</efg></CD></b></A></div>
+<div><our\u2603>Tag name contains Unicode characters</our\u2603></div>
+<div><a \u2603="snowman">Attribute name contains Unicode characters</a></div>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+"""
+
+
+class SoupTest(unittest.TestCase):
+
+    @property
+    def default_builder(self):
+        return default_builder
+
+    def soup(self, markup, **kwargs):
+        """Build a Beautiful Soup object from markup."""
+        builder = kwargs.pop('builder', self.default_builder)
+        return BeautifulSoup(markup, builder=builder, **kwargs)
+
+    def document_for(self, markup, **kwargs):
+        """Turn an HTML fragment into a document.
+
+        The details depend on the builder.
+        """
+        return self.default_builder(**kwargs).test_fragment_to_document(markup)
+
+    def assertSoupEquals(self, to_parse, compare_parsed_to=None):
+        builder = self.default_builder
+        obj = BeautifulSoup(to_parse, builder=builder)
+        if compare_parsed_to is None:
+            compare_parsed_to = to_parse
+
+        self.assertEqual(obj.decode(), self.document_for(compare_parsed_to))
+
+    def assertConnectedness(self, element):
+        """Ensure that next_element and previous_element are properly
+        set for all descendants of the given element.
+        """
+        earlier = None
+        for e in element.descendants:
+            if earlier:
+                self.assertEqual(e, earlier.next_element)
+                self.assertEqual(earlier, e.previous_element)
+            earlier = e
+
+    def linkage_validator(self, el, _recursive_call=False):
+        """Ensure proper linkage throughout the document."""
+        descendant = None
+        # Document element should have no previous element or previous sibling.
+        # It also shouldn't have a next sibling.
+        if el.parent is None:
+            assert el.previous_element is None,\
+                "Bad previous_element\nNODE: {}\nPREV: {}\nEXPECTED: {}".format(
+                    el, el.previous_element, None
+                )
+            assert el.previous_sibling is None,\
+                "Bad previous_sibling\nNODE: {}\nPREV: {}\nEXPECTED: {}".format(
+                    el, el.previous_sibling, None
+                )
+            assert el.next_sibling is None,\
+                "Bad next_sibling\nNODE: {}\nNEXT: {}\nEXPECTED: {}".format(
+                    el, el.next_sibling, None
+                )
+
+        idx = 0
+        child = None
+        last_child = None
+        last_idx = len(el.contents) - 1
+        for child in el.contents:
+            descendant = None
+
+            # Parent should link next element to their first child
+            # That child should have no previous sibling
+            if idx == 0:
+                if el.parent is not None:
+                    assert el.next_element is child,\
+                       "Bad next_element\nNODE: {}\nNEXT: {}\nEXPECTED: {}".format(
+                            el, el.next_element, child
+                        )
+                    assert child.previous_element is el,\
+                       "Bad previous_element\nNODE: {}\nPREV: {}\nEXPECTED: {}".format(
+                            child, child.previous_element, el
+                        )
+                    assert child.previous_sibling is None,\
+                       "Bad previous_sibling\nNODE: {}\nPREV {}\nEXPECTED: {}".format(
+                            child, child.previous_sibling, None
+                        )
+
+            # If not the first child, previous index should link as sibling to this index
+            # Previous element should match the last index or the last bubbled up descendant
+            else:
+                assert child.previous_sibling is el.contents[idx - 1],\
+                    "Bad previous_sibling\nNODE: {}\nPREV {}\nEXPECTED {}".format(
+                        child, child.previous_sibling, el.contents[idx - 1]
+                    )
+                assert el.contents[idx - 1].next_sibling is child,\
+                    "Bad next_sibling\nNODE: {}\nNEXT {}\nEXPECTED {}".format(
+                        el.contents[idx - 1], el.contents[idx - 1].next_sibling, child
+                    )
+
+                if last_child is not None:
+                    assert child.previous_element is last_child,\
+                        "Bad previous_element\nNODE: {}\nPREV {}\nEXPECTED {}\nCONTENTS {}".format(
+                            child, child.previous_element, last_child, child.parent.contents
+                        )
+                    assert last_child.next_element is child,\
+                        "Bad next_element\nNODE: {}\nNEXT {}\nEXPECTED {}".format(
+                            last_child, last_child.next_element, child
+                        )
+
+            if isinstance(child, Tag) and child.contents:
+                descendant = self.linkage_validator(child, True)
+                # A bubbled up descendant should have no next siblings
+                assert descendant.next_sibling is None,\
+                    "Bad next_sibling\nNODE: {}\nNEXT {}\nEXPECTED {}".format(
+                        descendant, descendant.next_sibling, None
+                    )
+
+            # Mark last child as either the bubbled up descendant or the current child
+            if descendant is not None:
+                last_child = descendant
+            else:
+                last_child = child
+
+            # If last child, there are non next siblings
+            if idx == last_idx:
+                assert child.next_sibling is None,\
+                    "Bad next_sibling\nNODE: {}\nNEXT {}\nEXPECTED {}".format(
+                        child, child.next_sibling, None
+                    )
+            idx += 1
+
+        child = descendant if descendant is not None else child
+        if child is None:
+            child = el
+
+        if not _recursive_call and child is not None:
+            target = el
+            while True:
+                if target is None:
+                    assert child.next_element is None, \
+                        "Bad next_element\nNODE: {}\nNEXT {}\nEXPECTED {}".format(
+                            child, child.next_element, None
+                        )
+                    break
+                elif target.next_sibling is not None:
+                    assert child.next_element is target.next_sibling, \
+                        "Bad next_element\nNODE: {}\nNEXT {}\nEXPECTED {}".format(
+                            child, child.next_element, target.next_sibling
+                        )
+                    break
+                target = target.parent
+
+            # We are done, so nothing to return
+            return None
+        else:
+            # Return the child to the recursive caller
+            return child
+
+
+class HTMLTreeBuilderSmokeTest(object):
+
+    """A basic test of a treebuilder's competence.
+
+    Any HTML treebuilder, present or future, should be able to pass
+    these tests. With invalid markup, there's room for interpretation,
+    and different parsers can handle it differently. But with the
+    markup in these tests, there's not much room for interpretation.
+    """
+
+    def test_empty_element_tags(self):
+        """Verify that all HTML4 and HTML5 empty element (aka void element) tags
+        are handled correctly.
+        """
+        for name in [
+                'area', 'base', 'br', 'col', 'embed', 'hr', 'img', 'input', 'keygen', 'link', 'menuitem', 'meta', 'param', 'source', 'track', 'wbr',
+                'spacer', 'frame'
+        ]:
+            soup = self.soup("")
+            new_tag = soup.new_tag(name)
+            self.assertEqual(True, new_tag.is_empty_element)
+
+    def test_pickle_and_unpickle_identity(self):
+        # Pickling a tree, then unpickling it, yields a tree identical
+        # to the original.
+        tree = self.soup("<a><b>foo</a>")
+        dumped = pickle.dumps(tree, 2)
+        loaded = pickle.loads(dumped)
+        self.assertEqual(loaded.__class__, BeautifulSoup)
+        self.assertEqual(loaded.decode(), tree.decode())
+
+    def assertDoctypeHandled(self, doctype_fragment):
+        """Assert that a given doctype string is handled correctly."""
+        doctype_str, soup = self._document_with_doctype(doctype_fragment)
+
+        # Make sure a Doctype object was created.
+        doctype = soup.contents[0]
+        self.assertEqual(doctype.__class__, Doctype)
+        self.assertEqual(doctype, doctype_fragment)
+        self.assertEqual(str(soup)[:len(doctype_str)], doctype_str)
+
+        # Make sure that the doctype was correctly associated with the
+        # parse tree and that the rest of the document parsed.
+        self.assertEqual(soup.p.contents[0], 'foo')
+
+    def _document_with_doctype(self, doctype_fragment):
+        """Generate and parse a document with the given doctype."""
+        doctype = '<!DOCTYPE %s>' % doctype_fragment
+        markup = doctype + '\n<p>foo</p>'
+        soup = self.soup(markup)
+        return doctype, soup
+
+    def test_normal_doctypes(self):
+        """Make sure normal, everyday HTML doctypes are handled correctly."""
+        self.assertDoctypeHandled("html")
+        self.assertDoctypeHandled(
+            'html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"')
+
+    def test_empty_doctype(self):
+        soup = self.soup("<!DOCTYPE>")
+        doctype = soup.contents[0]
+        self.assertEqual("", doctype.strip())
+
+    def test_public_doctype_with_url(self):
+        doctype = 'html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"'
+        self.assertDoctypeHandled(doctype)
+
+    def test_system_doctype(self):
+        self.assertDoctypeHandled('foo SYSTEM "http://www.example.com/"')
+
+    def test_namespaced_system_doctype(self):
+        # We can handle a namespaced doctype with a system ID.
+        self.assertDoctypeHandled('xsl:stylesheet SYSTEM "htmlent.dtd"')
+
+    def test_namespaced_public_doctype(self):
+        # Test a namespaced doctype with a public id.
+        self.assertDoctypeHandled('xsl:stylesheet PUBLIC "htmlent.dtd"')
+
+    def test_real_xhtml_document(self):
+        """A real XHTML document should come out more or less the same as it went in."""
+        markup = b"""<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head><title>Hello.</title></head>
+<body>Goodbye.</body>
+</html>"""
+        soup = self.soup(markup)
+        self.assertEqual(
+            soup.encode("utf-8").replace(b"\n", b""),
+            markup.replace(b"\n", b""))
+
+    def test_namespaced_html(self):
+        """When a namespaced XML document is parsed as HTML it should
+        be treated as HTML with weird tag names.
+        """
+        markup = b"""<ns1:foo>content</ns1:foo><ns1:foo/><ns2:foo/>"""
+        soup = self.soup(markup)
+        self.assertEqual(2, len(soup.find_all("ns1:foo")))
+        
+    def test_processing_instruction(self):
+        # We test both Unicode and bytestring to verify that
+        # process_markup correctly sets processing_instruction_class
+        # even when the markup is already Unicode and there is no
+        # need to process anything.
+        markup = """<?PITarget PIContent?>"""
+        soup = self.soup(markup)
+        self.assertEqual(markup, soup.decode())
+
+        markup = b"""<?PITarget PIContent?>"""
+        soup = self.soup(markup)
+        self.assertEqual(markup, soup.encode("utf8"))
+
+    def test_deepcopy(self):
+        """Make sure you can copy the tree builder.
+
+        This is important because the builder is part of a
+        BeautifulSoup object, and we want to be able to copy that.
+        """
+        copy.deepcopy(self.default_builder)
+
+    def test_p_tag_is_never_empty_element(self):
+        """A <p> tag is never designated as an empty-element tag.
+
+        Even if the markup shows it as an empty-element tag, it
+        shouldn't be presented that way.
+        """
+        soup = self.soup("<p/>")
+        self.assertFalse(soup.p.is_empty_element)
+        self.assertEqual(str(soup.p), "<p></p>")
+
+    def test_unclosed_tags_get_closed(self):
+        """A tag that's not closed by the end of the document should be closed.
+
+        This applies to all tags except empty-element tags.
+        """
+        self.assertSoupEquals("<p>", "<p></p>")
+        self.assertSoupEquals("<b>", "<b></b>")
+
+        self.assertSoupEquals("<br>", "<br/>")
+
+    def test_br_is_always_empty_element_tag(self):
+        """A <br> tag is designated as an empty-element tag.
+
+        Some parsers treat <br></br> as one <br/> tag, some parsers as
+        two tags, but it should always be an empty-element tag.
+        """
+        soup = self.soup("<br></br>")
+        self.assertTrue(soup.br.is_empty_element)
+        self.assertEqual(str(soup.br), "<br/>")
+
+    def test_nested_formatting_elements(self):
+        self.assertSoupEquals("<em><em></em></em>")
+
+    def test_double_head(self):
+        html = '''<!DOCTYPE html>
+<html>
+<head>
+<title>Ordinary HEAD element test</title>
+</head>
+<script type="text/javascript">
+alert("Help!");
+</script>
+<body>
+Hello, world!
+</body>
+</html>
+'''
+        soup = self.soup(html)
+        self.assertEqual("text/javascript", soup.find('script')['type'])
+
+    def test_comment(self):
+        # Comments are represented as Comment objects.
+        markup = "<p>foo<!--foobar-->baz</p>"
+        self.assertSoupEquals(markup)
+
+        soup = self.soup(markup)
+        comment = soup.find(text="foobar")
+        self.assertEqual(comment.__class__, Comment)
+
+        # The comment is properly integrated into the tree.
+        foo = soup.find(text="foo")
+        self.assertEqual(comment, foo.next_element)
+        baz = soup.find(text="baz")
+        self.assertEqual(comment, baz.previous_element)
+
+    def test_preserved_whitespace_in_pre_and_textarea(self):
+        """Whitespace must be preserved in <pre> and <textarea> tags,
+        even if that would mean not prettifying the markup.
+        """
+        pre_markup = "<pre>   </pre>"
+        textarea_markup = "<textarea> woo\nwoo  </textarea>"
+        self.assertSoupEquals(pre_markup)
+        self.assertSoupEquals(textarea_markup)
+
+        soup = self.soup(pre_markup)
+        self.assertEqual(soup.pre.prettify(), pre_markup)
+
+        soup = self.soup(textarea_markup)
+        self.assertEqual(soup.textarea.prettify(), textarea_markup)
+
+        soup = self.soup("<textarea></textarea>")
+        self.assertEqual(soup.textarea.prettify(), "<textarea></textarea>")
+
+    def test_nested_inline_elements(self):
+        """Inline elements can be nested indefinitely."""
+        b_tag = "<b>Inside a B tag</b>"
+        self.assertSoupEquals(b_tag)
+
+        nested_b_tag = "<p>A <i>nested <b>tag</b></i></p>"
+        self.assertSoupEquals(nested_b_tag)
+
+        double_nested_b_tag = "<p>A <a>doubly <i>nested <b>tag</b></i></a></p>"
+        self.assertSoupEquals(nested_b_tag)
+
+    def test_nested_block_level_elements(self):
+        """Block elements can be nested."""
+        soup = self.soup('<blockquote><p><b>Foo</b></p></blockquote>')
+        blockquote = soup.blockquote
+        self.assertEqual(blockquote.p.b.string, 'Foo')
+        self.assertEqual(blockquote.b.string, 'Foo')
+
+    def test_correctly_nested_tables(self):
+        """One table can go inside another one."""
+        markup = ('<table id="1">'
+                  '<tr>'
+                  "<td>Here's another table:"
+                  '<table id="2">'
+                  '<tr><td>foo</td></tr>'
+                  '</table></td>')
+
+        self.assertSoupEquals(
+            markup,
+            '<table id="1"><tr><td>Here\'s another table:'
+            '<table id="2"><tr><td>foo</td></tr></table>'
+            '</td></tr></table>')
+
+        self.assertSoupEquals(
+            "<table><thead><tr><td>Foo</td></tr></thead>"
+            "<tbody><tr><td>Bar</td></tr></tbody>"
+            "<tfoot><tr><td>Baz</td></tr></tfoot></table>")
+
+    def test_multivalued_attribute_with_whitespace(self):
+        # Whitespace separating the values of a multi-valued attribute
+        # should be ignored.
+
+        markup = '<div class=" foo bar	 "></a>'
+        soup = self.soup(markup)
+        self.assertEqual(['foo', 'bar'], soup.div['class'])
+
+        # If you search by the literal name of the class it's like the whitespace
+        # wasn't there.
+        self.assertEqual(soup.div, soup.find('div', class_="foo bar"))
+        
+    def test_deeply_nested_multivalued_attribute(self):
+        # html5lib can set the attributes of the same tag many times
+        # as it rearranges the tree. This has caused problems with
+        # multivalued attributes.
+        markup = '<table><div><div class="css"></div></div></table>'
+        soup = self.soup(markup)
+        self.assertEqual(["css"], soup.div.div['class'])
+
+    def test_multivalued_attribute_on_html(self):
+        # html5lib uses a different API to set the attributes ot the
+        # <html> tag. This has caused problems with multivalued
+        # attributes.
+        markup = '<html class="a b"></html>'
+        soup = self.soup(markup)
+        self.assertEqual(["a", "b"], soup.html['class'])
+
+    def test_angle_brackets_in_attribute_values_are_escaped(self):
+        self.assertSoupEquals('<a b="<a>"></a>', '<a b="&lt;a&gt;"></a>')
+
+    def test_strings_resembling_character_entity_references(self):
+        # "&T" and "&p" look like incomplete character entities, but they are
+        # not.
+        self.assertSoupEquals(
+            "<p>&bull; AT&T is in the s&p 500</p>",
+            "<p>\u2022 AT&amp;T is in the s&amp;p 500</p>"
+        )
+
+    def test_apos_entity(self):
+        self.assertSoupEquals(
+            "<p>Bob&apos;s Bar</p>",
+            "<p>Bob's Bar</p>",
+        )
+        
+    def test_entities_in_foreign_document_encoding(self):
+        # &#147; and &#148; are invalid numeric entities referencing
+        # Windows-1252 characters. &#45; references a character common
+        # to Windows-1252 and Unicode, and &#9731; references a
+        # character only found in Unicode.
+        #
+        # All of these entities should be converted to Unicode
+        # characters.
+        markup = "<p>&#147;Hello&#148; &#45;&#9731;</p>"
+        soup = self.soup(markup)
+        self.assertEqual("“Hello” -☃", soup.p.string)
+        
+    def test_entities_in_attributes_converted_to_unicode(self):
+        expect = '<p id="pi\N{LATIN SMALL LETTER N WITH TILDE}ata"></p>'
+        self.assertSoupEquals('<p id="pi&#241;ata"></p>', expect)
+        self.assertSoupEquals('<p id="pi&#xf1;ata"></p>', expect)
+        self.assertSoupEquals('<p id="pi&#Xf1;ata"></p>', expect)
+        self.assertSoupEquals('<p id="pi&ntilde;ata"></p>', expect)
+
+    def test_entities_in_text_converted_to_unicode(self):
+        expect = '<p>pi\N{LATIN SMALL LETTER N WITH TILDE}ata</p>'
+        self.assertSoupEquals("<p>pi&#241;ata</p>", expect)
+        self.assertSoupEquals("<p>pi&#xf1;ata</p>", expect)
+        self.assertSoupEquals("<p>pi&#Xf1;ata</p>", expect)
+        self.assertSoupEquals("<p>pi&ntilde;ata</p>", expect)
+
+    def test_quot_entity_converted_to_quotation_mark(self):
+        self.assertSoupEquals("<p>I said &quot;good day!&quot;</p>",
+                              '<p>I said "good day!"</p>')
+
+    def test_out_of_range_entity(self):
+        expect = "\N{REPLACEMENT CHARACTER}"
+        self.assertSoupEquals("&#10000000000000;", expect)
+        self.assertSoupEquals("&#x10000000000000;", expect)
+        self.assertSoupEquals("&#1000000000;", expect)
+        
+    def test_multipart_strings(self):
+        "Mostly to prevent a recurrence of a bug in the html5lib treebuilder."
+        soup = self.soup("<html><h2>\nfoo</h2><p></p></html>")
+        self.assertEqual("p", soup.h2.string.next_element.name)
+        self.assertEqual("p", soup.p.name)
+        self.assertConnectedness(soup)
+
+    def test_empty_element_tags(self):
+        """Verify consistent handling of empty-element tags,
+        no matter how they come in through the markup.
+        """
+        self.assertSoupEquals('<br/><br/><br/>', "<br/><br/><br/>")
+        self.assertSoupEquals('<br /><br /><br />', "<br/><br/><br/>")
+        
+    def test_head_tag_between_head_and_body(self):
+        "Prevent recurrence of a bug in the html5lib treebuilder."
+        content = """<html><head></head>
+  <link></link>
+  <body>foo</body>
+</html>
+"""
+        soup = self.soup(content)
+        self.assertNotEqual(None, soup.html.body)
+        self.assertConnectedness(soup)
+
+    def test_multiple_copies_of_a_tag(self):
+        "Prevent recurrence of a bug in the html5lib treebuilder."
+        content = """<!DOCTYPE html>
+<html>
+ <body>
+   <article id="a" >
+   <div><a href="1"></div>
+   <footer>
+     <a href="2"></a>
+   </footer>
+  </article>
+  </body>
+</html>
+"""
+        soup = self.soup(content)
+        self.assertConnectedness(soup.article)
+
+    def test_basic_namespaces(self):
+        """Parsers don't need to *understand* namespaces, but at the
+        very least they should not choke on namespaces or lose
+        data."""
+
+        markup = b'<html xmlns="http://www.w3.org/1999/xhtml" xmlns:mathml="http://www.w3.org/1998/Math/MathML" xmlns:svg="http://www.w3.org/2000/svg"><head></head><body><mathml:msqrt>4</mathml:msqrt><b svg:fill="red"></b></body></html>'
+        soup = self.soup(markup)
+        self.assertEqual(markup, soup.encode())
+        html = soup.html
+        self.assertEqual('http://www.w3.org/1999/xhtml', soup.html['xmlns'])
+        self.assertEqual(
+            'http://www.w3.org/1998/Math/MathML', soup.html['xmlns:mathml'])
+        self.assertEqual(
+            'http://www.w3.org/2000/svg', soup.html['xmlns:svg'])
+
+    def test_multivalued_attribute_value_becomes_list(self):
+        markup = b'<a class="foo bar">'
+        soup = self.soup(markup)
+        self.assertEqual(['foo', 'bar'], soup.a['class'])
+
+    #
+    # Generally speaking, tests below this point are more tests of
+    # Beautiful Soup than tests of the tree builders. But parsers are
+    # weird, so we run these tests separately for every tree builder
+    # to detect any differences between them.
+    #
+
+    def test_can_parse_unicode_document(self):
+        # A seemingly innocuous document... but it's in Unicode! And
+        # it contains characters that can't be represented in the
+        # encoding found in the  declaration! The horror!
+        markup = '<html><head><meta encoding="euc-jp"></head><body>Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!</body>'
+        soup = self.soup(markup)
+        self.assertEqual('Sacr\xe9 bleu!', soup.body.string)
+
+    def test_soupstrainer(self):
+        """Parsers should be able to work with SoupStrainers."""
+        strainer = SoupStrainer("b")
+        soup = self.soup("A <b>bold</b> <meta/> <i>statement</i>",
+                         parse_only=strainer)
+        self.assertEqual(soup.decode(), "<b>bold</b>")
+
+    def test_single_quote_attribute_values_become_double_quotes(self):
+        self.assertSoupEquals("<foo attr='bar'></foo>",
+                              '<foo attr="bar"></foo>')
+
+    def test_attribute_values_with_nested_quotes_are_left_alone(self):
+        text = """<foo attr='bar "brawls" happen'>a</foo>"""
+        self.assertSoupEquals(text)
+
+    def test_attribute_values_with_double_nested_quotes_get_quoted(self):
+        text = """<foo attr='bar "brawls" happen'>a</foo>"""
+        soup = self.soup(text)
+        soup.foo['attr'] = 'Brawls happen at "Bob\'s Bar"'
+        self.assertSoupEquals(
+            soup.foo.decode(),
+            """<foo attr="Brawls happen at &quot;Bob\'s Bar&quot;">a</foo>""")
+
+    def test_ampersand_in_attribute_value_gets_escaped(self):
+        self.assertSoupEquals('<this is="really messed up & stuff"></this>',
+                              '<this is="really messed up &amp; stuff"></this>')
+
+        self.assertSoupEquals(
+            '<a href="http://example.org?a=1&b=2;3">foo</a>',
+            '<a href="http://example.org?a=1&amp;b=2;3">foo</a>')
+
+    def test_escaped_ampersand_in_attribute_value_is_left_alone(self):
+        self.assertSoupEquals('<a href="http://example.org?a=1&amp;b=2;3"></a>')
+
+    def test_entities_in_strings_converted_during_parsing(self):
+        # Both XML and HTML entities are converted to Unicode characters
+        # during parsing.
+        text = "<p>&lt;&lt;sacr&eacute;&#32;bleu!&gt;&gt;</p>"
+        expected = "<p>&lt;&lt;sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</p>"
+        self.assertSoupEquals(text, expected)
+
+    def test_smart_quotes_converted_on_the_way_in(self):
+        # Microsoft smart quotes are converted to Unicode characters during
+        # parsing.
+        quote = b"<p>\x91Foo\x92</p>"
+        soup = self.soup(quote)
+        self.assertEqual(
+            soup.p.string,
+            "\N{LEFT SINGLE QUOTATION MARK}Foo\N{RIGHT SINGLE QUOTATION MARK}")
+
+    def test_non_breaking_spaces_converted_on_the_way_in(self):
+        soup = self.soup("<a>&nbsp;&nbsp;</a>")
+        self.assertEqual(soup.a.string, "\N{NO-BREAK SPACE}" * 2)
+
+    def test_entities_converted_on_the_way_out(self):
+        text = "<p>&lt;&lt;sacr&eacute;&#32;bleu!&gt;&gt;</p>"
+        expected = "<p>&lt;&lt;sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</p>".encode("utf-8")
+        soup = self.soup(text)
+        self.assertEqual(soup.p.encode("utf-8"), expected)
+
+    def test_real_iso_latin_document(self):
+        # Smoke test of interrelated functionality, using an
+        # easy-to-understand document.
+
+        # Here it is in Unicode. Note that it claims to be in ISO-Latin-1.
+        unicode_html = '<html><head><meta content="text/html; charset=ISO-Latin-1" http-equiv="Content-type"/></head><body><p>Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!</p></body></html>'
+
+        # That's because we're going to encode it into ISO-Latin-1, and use
+        # that to test.
+        iso_latin_html = unicode_html.encode("iso-8859-1")
+
+        # Parse the ISO-Latin-1 HTML.
+        soup = self.soup(iso_latin_html)
+        # Encode it to UTF-8.
+        result = soup.encode("utf-8")
+
+        # What do we expect the result to look like? Well, it would
+        # look like unicode_html, except that the META tag would say
+        # UTF-8 instead of ISO-Latin-1.
+        expected = unicode_html.replace("ISO-Latin-1", "utf-8")
+
+        # And, of course, it would be in UTF-8, not Unicode.
+        expected = expected.encode("utf-8")
+
+        # Ta-da!
+        self.assertEqual(result, expected)
+
+    def test_real_shift_jis_document(self):
+        # Smoke test to make sure the parser can handle a document in
+        # Shift-JIS encoding, without choking.
+        shift_jis_html = (
+            b'<html><head></head><body><pre>'
+            b'\x82\xb1\x82\xea\x82\xcdShift-JIS\x82\xc5\x83R\x81[\x83f'
+            b'\x83B\x83\x93\x83O\x82\xb3\x82\xea\x82\xbd\x93\xfa\x96{\x8c'
+            b'\xea\x82\xcc\x83t\x83@\x83C\x83\x8b\x82\xc5\x82\xb7\x81B'
+            b'</pre></body></html>')
+        unicode_html = shift_jis_html.decode("shift-jis")
+        soup = self.soup(unicode_html)
+
+        # Make sure the parse tree is correctly encoded to various
+        # encodings.
+        self.assertEqual(soup.encode("utf-8"), unicode_html.encode("utf-8"))
+        self.assertEqual(soup.encode("euc_jp"), unicode_html.encode("euc_jp"))
+
+    def test_real_hebrew_document(self):
+        # A real-world test to make sure we can convert ISO-8859-9 (a
+        # Hebrew encoding) to UTF-8.
+        hebrew_document = b'<html><head><title>Hebrew (ISO 8859-8) in Visual Directionality</title></head><body><h1>Hebrew (ISO 8859-8) in Visual Directionality</h1>\xed\xe5\xec\xf9</body></html>'
+        soup = self.soup(
+            hebrew_document, from_encoding="iso8859-8")
+        # Some tree builders call it iso8859-8, others call it iso-8859-9.
+        # That's not a difference we really care about.
+        assert soup.original_encoding in ('iso8859-8', 'iso-8859-8')
+        self.assertEqual(
+            soup.encode('utf-8'),
+            hebrew_document.decode("iso8859-8").encode("utf-8"))
+
+    def test_meta_tag_reflects_current_encoding(self):
+        # Here's the <meta> tag saying that a document is
+        # encoded in Shift-JIS.
+        meta_tag = ('<meta content="text/html; charset=x-sjis" '
+                    'http-equiv="Content-type"/>')
+
+        # Here's a document incorporating that meta tag.
+        shift_jis_html = (
+            '<html><head>\n%s\n'
+            '<meta http-equiv="Content-language" content="ja"/>'
+            '</head><body>Shift-JIS markup goes here.') % meta_tag
+        soup = self.soup(shift_jis_html)
+
+        # Parse the document, and the charset is seemingly unaffected.
+        parsed_meta = soup.find('meta', {'http-equiv': 'Content-type'})
+        content = parsed_meta['content']
+        self.assertEqual('text/html; charset=x-sjis', content)
+
+        # But that value is actually a ContentMetaAttributeValue object.
+        self.assertTrue(isinstance(content, ContentMetaAttributeValue))
+
+        # And it will take on a value that reflects its current
+        # encoding.
+        self.assertEqual('text/html; charset=utf8', content.encode("utf8"))
+
+        # For the rest of the story, see TestSubstitutions in
+        # test_tree.py.
+
+    def test_html5_style_meta_tag_reflects_current_encoding(self):
+        # Here's the <meta> tag saying that a document is
+        # encoded in Shift-JIS.
+        meta_tag = ('<meta id="encoding" charset="x-sjis" />')
+
+        # Here's a document incorporating that meta tag.
+        shift_jis_html = (
+            '<html><head>\n%s\n'
+            '<meta http-equiv="Content-language" content="ja"/>'
+            '</head><body>Shift-JIS markup goes here.') % meta_tag
+        soup = self.soup(shift_jis_html)
+
+        # Parse the document, and the charset is seemingly unaffected.
+        parsed_meta = soup.find('meta', id="encoding")
+        charset = parsed_meta['charset']
+        self.assertEqual('x-sjis', charset)
+
+        # But that value is actually a CharsetMetaAttributeValue object.
+        self.assertTrue(isinstance(charset, CharsetMetaAttributeValue))
+
+        # And it will take on a value that reflects its current
+        # encoding.
+        self.assertEqual('utf8', charset.encode("utf8"))
+
+    def test_tag_with_no_attributes_can_have_attributes_added(self):
+        data = self.soup("<a>text</a>")
+        data.a['foo'] = 'bar'
+        self.assertEqual('<a foo="bar">text</a>', data.a.decode())
+
+    def test_worst_case(self):
+        """Test the worst case (currently) for linking issues."""
+
+        soup = self.soup(BAD_DOCUMENT)
+        self.linkage_validator(soup)
+
+
+class XMLTreeBuilderSmokeTest(object):
+
+    def test_pickle_and_unpickle_identity(self):
+        # Pickling a tree, then unpickling it, yields a tree identical
+        # to the original.
+        tree = self.soup("<a><b>foo</a>")
+        dumped = pickle.dumps(tree, 2)
+        loaded = pickle.loads(dumped)
+        self.assertEqual(loaded.__class__, BeautifulSoup)
+        self.assertEqual(loaded.decode(), tree.decode())
+
+    def test_docstring_generated(self):
+        soup = self.soup("<root/>")
+        self.assertEqual(
+            soup.encode(), b'<?xml version="1.0" encoding="utf-8"?>\n<root/>')
+
+    def test_xml_declaration(self):
+        markup = b"""<?xml version="1.0" encoding="utf8"?>\n<foo/>"""
+        soup = self.soup(markup)
+        self.assertEqual(markup, soup.encode("utf8"))
+
+    def test_processing_instruction(self):
+        markup = b"""<?xml version="1.0" encoding="utf8"?>\n<?PITarget PIContent?>"""
+        soup = self.soup(markup)
+        self.assertEqual(markup, soup.encode("utf8"))
+
+    def test_real_xhtml_document(self):
+        """A real XHTML document should come out *exactly* the same as it went in."""
+        markup = b"""<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head><title>Hello.</title></head>
+<body>Goodbye.</body>
+</html>"""
+        soup = self.soup(markup)
+        self.assertEqual(
+            soup.encode("utf-8"), markup)
+
+    def test_nested_namespaces(self):
+        doc = b"""<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
+<parent xmlns="http://ns1/">
+<child xmlns="http://ns2/" xmlns:ns3="http://ns3/">
+<grandchild ns3:attr="value" xmlns="http://ns4/"/>
+</child>
+</parent>"""
+        soup = self.soup(doc)
+        self.assertEqual(doc, soup.encode())
+        
+    def test_formatter_processes_script_tag_for_xml_documents(self):
+        doc = """
+  <script type="text/javascript">
+  </script>
+"""
+        soup = BeautifulSoup(doc, "lxml-xml")
+        # lxml would have stripped this while parsing, but we can add
+        # it later.
+        soup.script.string = 'console.log("< < hey > > ");'
+        encoded = soup.encode()
+        self.assertTrue(b"&lt; &lt; hey &gt; &gt;" in encoded)
+
+    def test_can_parse_unicode_document(self):
+        markup = '<?xml version="1.0" encoding="euc-jp"><root>Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!</root>'
+        soup = self.soup(markup)
+        self.assertEqual('Sacr\xe9 bleu!', soup.root.string)
+
+    def test_popping_namespaced_tag(self):
+        markup = '<rss xmlns:dc="foo"><dc:creator>b</dc:creator><dc:date>2012-07-02T20:33:42Z</dc:date><dc:rights>c</dc:rights><image>d</image></rss>'
+        soup = self.soup(markup)
+        self.assertEqual(
+            str(soup.rss), markup)
+
+    def test_docstring_includes_correct_encoding(self):
+        soup = self.soup("<root/>")
+        self.assertEqual(
+            soup.encode("latin1"),
+            b'<?xml version="1.0" encoding="latin1"?>\n<root/>')
+
+    def test_large_xml_document(self):
+        """A large XML document should come out the same as it went in."""
+        markup = (b'<?xml version="1.0" encoding="utf-8"?>\n<root>'
+                  + b'0' * (2**12)
+                  + b'</root>')
+        soup = self.soup(markup)
+        self.assertEqual(soup.encode("utf-8"), markup)
+
+
+    def test_tags_are_empty_element_if_and_only_if_they_are_empty(self):
+        self.assertSoupEquals("<p>", "<p/>")
+        self.assertSoupEquals("<p>foo</p>")
+
+    def test_namespaces_are_preserved(self):
+        markup = '<root xmlns:a="http://example.com/" xmlns:b="http://example.net/"><a:foo>This tag is in the a namespace</a:foo><b:foo>This tag is in the b namespace</b:foo></root>'
+        soup = self.soup(markup)
+        root = soup.root
+        self.assertEqual("http://example.com/", root['xmlns:a'])
+        self.assertEqual("http://example.net/", root['xmlns:b'])
+
+    def test_closing_namespaced_tag(self):
+        markup = '<p xmlns:dc="http://purl.org/dc/elements/1.1/"><dc:date>20010504</dc:date></p>'
+        soup = self.soup(markup)
+        self.assertEqual(str(soup.p), markup)
+
+    def test_namespaced_attributes(self):
+        markup = '<foo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><bar xsi:schemaLocation="http://www.example.com"/></foo>'
+        soup = self.soup(markup)
+        self.assertEqual(str(soup.foo), markup)
+
+    def test_namespaced_attributes_xml_namespace(self):
+        markup = '<foo xml:lang="fr">bar</foo>'
+        soup = self.soup(markup)
+        self.assertEqual(str(soup.foo), markup)
+
+    def test_find_by_prefixed_name(self):
+        doc = """<?xml version="1.0" encoding="utf-8"?>
+<Document xmlns="http://example.com/ns0"
+    xmlns:ns1="http://example.com/ns1"
+    xmlns:ns2="http://example.com/ns2"
+    <ns1:tag>foo</ns1:tag>
+    <ns1:tag>bar</ns1:tag>
+    <ns2:tag key="value">baz</ns2:tag>
+</Document>
+"""
+        soup = self.soup(doc)
+
+        # There are three <tag> tags.
+        self.assertEqual(3, len(soup.find_all('tag')))
+
+        # But two of them are ns1:tag and one of them is ns2:tag.
+        self.assertEqual(2, len(soup.find_all('ns1:tag')))
+        self.assertEqual(1, len(soup.find_all('ns2:tag')))
+        
+        self.assertEqual(1, len(soup.find_all('ns2:tag', key='value')))
+        self.assertEqual(3, len(soup.find_all(['ns1:tag', 'ns2:tag'])))
+        
+    def test_copy_tag_preserves_namespace(self):
+        xml = """<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<w:document xmlns:w="http://example.com/ns0"/>"""
+    
+        soup = self.soup(xml)
+        tag = soup.document
+        duplicate = copy.copy(tag)
+
+        # The two tags have the same namespace prefix.
+        self.assertEqual(tag.prefix, duplicate.prefix)
+
+    def test_worst_case(self):
+        """Test the worst case (currently) for linking issues."""
+
+        soup = self.soup(BAD_DOCUMENT)
+        self.linkage_validator(soup)
+
+
+class HTML5TreeBuilderSmokeTest(HTMLTreeBuilderSmokeTest):
+    """Smoke test for a tree builder that supports HTML5."""
+
+    def test_real_xhtml_document(self):
+        # Since XHTML is not HTML5, HTML5 parsers are not tested to handle
+        # XHTML documents in any particular way.
+        pass
+
+    def test_html_tags_have_namespace(self):
+        markup = "<a>"
+        soup = self.soup(markup)
+        self.assertEqual("http://www.w3.org/1999/xhtml", soup.a.namespace)
+
+    def test_svg_tags_have_namespace(self):
+        markup = '<svg><circle/></svg>'
+        soup = self.soup(markup)
+        namespace = "http://www.w3.org/2000/svg"
+        self.assertEqual(namespace, soup.svg.namespace)
+        self.assertEqual(namespace, soup.circle.namespace)
+
+
+    def test_mathml_tags_have_namespace(self):
+        markup = '<math><msqrt>5</msqrt></math>'
+        soup = self.soup(markup)
+        namespace = 'http://www.w3.org/1998/Math/MathML'
+        self.assertEqual(namespace, soup.math.namespace)
+        self.assertEqual(namespace, soup.msqrt.namespace)
+
+    def test_xml_declaration_becomes_comment(self):
+        markup = '<?xml version="1.0" encoding="utf-8"?><html></html>'
+        soup = self.soup(markup)
+        self.assertTrue(isinstance(soup.contents[0], Comment))
+        self.assertEqual(soup.contents[0], '?xml version="1.0" encoding="utf-8"?')
+        self.assertEqual("html", soup.contents[0].next_element.name)
+
+def skipIf(condition, reason):
+   def nothing(test, *args, **kwargs):
+       return None
+
+   def decorator(test_item):
+       if condition:
+           return nothing
+       else:
+           return test_item
+
+   return decorator
diff --git a/libs/bs4/tests/__init__.py b/libs/bs4/tests/__init__.py
new file mode 100644
index 000000000..142c8cc3f
--- /dev/null
+++ b/libs/bs4/tests/__init__.py
@@ -0,0 +1 @@
+"The beautifulsoup tests."
diff --git a/libs/bs4/tests/test_builder_registry.py b/libs/bs4/tests/test_builder_registry.py
new file mode 100644
index 000000000..90cad8293
--- /dev/null
+++ b/libs/bs4/tests/test_builder_registry.py
@@ -0,0 +1,147 @@
+"""Tests of the builder registry."""
+
+import unittest
+import warnings
+
+from bs4 import BeautifulSoup
+from bs4.builder import (
+    builder_registry as registry,
+    HTMLParserTreeBuilder,
+    TreeBuilderRegistry,
+)
+
+try:
+    from bs4.builder import HTML5TreeBuilder
+    HTML5LIB_PRESENT = True
+except ImportError:
+    HTML5LIB_PRESENT = False
+
+try:
+    from bs4.builder import (
+        LXMLTreeBuilderForXML,
+        LXMLTreeBuilder,
+        )
+    LXML_PRESENT = True
+except ImportError:
+    LXML_PRESENT = False
+
+
+class BuiltInRegistryTest(unittest.TestCase):
+    """Test the built-in registry with the default builders registered."""
+
+    def test_combination(self):
+        if LXML_PRESENT:
+            self.assertEqual(registry.lookup('fast', 'html'),
+                             LXMLTreeBuilder)
+
+        if LXML_PRESENT:
+            self.assertEqual(registry.lookup('permissive', 'xml'),
+                             LXMLTreeBuilderForXML)
+        self.assertEqual(registry.lookup('strict', 'html'),
+                          HTMLParserTreeBuilder)
+        if HTML5LIB_PRESENT:
+            self.assertEqual(registry.lookup('html5lib', 'html'),
+                              HTML5TreeBuilder)
+
+    def test_lookup_by_markup_type(self):
+        if LXML_PRESENT:
+            self.assertEqual(registry.lookup('html'), LXMLTreeBuilder)
+            self.assertEqual(registry.lookup('xml'), LXMLTreeBuilderForXML)
+        else:
+            self.assertEqual(registry.lookup('xml'), None)
+            if HTML5LIB_PRESENT:
+                self.assertEqual(registry.lookup('html'), HTML5TreeBuilder)
+            else:
+                self.assertEqual(registry.lookup('html'), HTMLParserTreeBuilder)
+
+    def test_named_library(self):
+        if LXML_PRESENT:
+            self.assertEqual(registry.lookup('lxml', 'xml'),
+                             LXMLTreeBuilderForXML)
+            self.assertEqual(registry.lookup('lxml', 'html'),
+                             LXMLTreeBuilder)
+        if HTML5LIB_PRESENT:
+            self.assertEqual(registry.lookup('html5lib'),
+                              HTML5TreeBuilder)
+
+        self.assertEqual(registry.lookup('html.parser'),
+                          HTMLParserTreeBuilder)
+
+    def test_beautifulsoup_constructor_does_lookup(self):
+
+        with warnings.catch_warnings(record=True) as w:
+            # This will create a warning about not explicitly
+            # specifying a parser, but we'll ignore it.
+
+            # You can pass in a string.
+            BeautifulSoup("", features="html")
+            # Or a list of strings.
+            BeautifulSoup("", features=["html", "fast"])
+
+        # You'll get an exception if BS can't find an appropriate
+        # builder.
+        self.assertRaises(ValueError, BeautifulSoup,
+                          "", features="no-such-feature")
+
+class RegistryTest(unittest.TestCase):
+    """Test the TreeBuilderRegistry class in general."""
+
+    def setUp(self):
+        self.registry = TreeBuilderRegistry()
+
+    def builder_for_features(self, *feature_list):
+        cls = type('Builder_' + '_'.join(feature_list),
+                   (object,), {'features' : feature_list})
+
+        self.registry.register(cls)
+        return cls
+
+    def test_register_with_no_features(self):
+        builder = self.builder_for_features()
+
+        # Since the builder advertises no features, you can't find it
+        # by looking up features.
+        self.assertEqual(self.registry.lookup('foo'), None)
+
+        # But you can find it by doing a lookup with no features, if
+        # this happens to be the only registered builder.
+        self.assertEqual(self.registry.lookup(), builder)
+
+    def test_register_with_features_makes_lookup_succeed(self):
+        builder = self.builder_for_features('foo', 'bar')
+        self.assertEqual(self.registry.lookup('foo'), builder)
+        self.assertEqual(self.registry.lookup('bar'), builder)
+
+    def test_lookup_fails_when_no_builder_implements_feature(self):
+        builder = self.builder_for_features('foo', 'bar')
+        self.assertEqual(self.registry.lookup('baz'), None)
+
+    def test_lookup_gets_most_recent_registration_when_no_feature_specified(self):
+        builder1 = self.builder_for_features('foo')
+        builder2 = self.builder_for_features('bar')
+        self.assertEqual(self.registry.lookup(), builder2)
+
+    def test_lookup_fails_when_no_tree_builders_registered(self):
+        self.assertEqual(self.registry.lookup(), None)
+
+    def test_lookup_gets_most_recent_builder_supporting_all_features(self):
+        has_one = self.builder_for_features('foo')
+        has_the_other = self.builder_for_features('bar')
+        has_both_early = self.builder_for_features('foo', 'bar', 'baz')
+        has_both_late = self.builder_for_features('foo', 'bar', 'quux')
+        lacks_one = self.builder_for_features('bar')
+        has_the_other = self.builder_for_features('foo')
+
+        # There are two builders featuring 'foo' and 'bar', but
+        # the one that also features 'quux' was registered later.
+        self.assertEqual(self.registry.lookup('foo', 'bar'),
+                          has_both_late)
+
+        # There is only one builder featuring 'foo', 'bar', and 'baz'.
+        self.assertEqual(self.registry.lookup('foo', 'bar', 'baz'),
+                          has_both_early)
+
+    def test_lookup_fails_when_cannot_reconcile_requested_features(self):
+        builder1 = self.builder_for_features('foo', 'bar')
+        builder2 = self.builder_for_features('foo', 'baz')
+        self.assertEqual(self.registry.lookup('bar', 'baz'), None)
diff --git a/libs/bs4/tests/test_docs.py b/libs/bs4/tests/test_docs.py
new file mode 100644
index 000000000..5b9f67709
--- /dev/null
+++ b/libs/bs4/tests/test_docs.py
@@ -0,0 +1,36 @@
+"Test harness for doctests."
+
+# pylint: disable-msg=E0611,W0142
+
+__metaclass__ = type
+__all__ = [
+    'additional_tests',
+    ]
+
+import atexit
+import doctest
+import os
+#from pkg_resources import (
+#    resource_filename, resource_exists, resource_listdir, cleanup_resources)
+import unittest
+
+DOCTEST_FLAGS = (
+    doctest.ELLIPSIS |
+    doctest.NORMALIZE_WHITESPACE |
+    doctest.REPORT_NDIFF)
+
+
+# def additional_tests():
+#     "Run the doc tests (README.txt and docs/*, if any exist)"
+#     doctest_files = [
+#         os.path.abspath(resource_filename('bs4', 'README.txt'))]
+#     if resource_exists('bs4', 'docs'):
+#         for name in resource_listdir('bs4', 'docs'):
+#             if name.endswith('.txt'):
+#                 doctest_files.append(
+#                     os.path.abspath(
+#                         resource_filename('bs4', 'docs/%s' % name)))
+#     kwargs = dict(module_relative=False, optionflags=DOCTEST_FLAGS)
+#     atexit.register(cleanup_resources)
+#     return unittest.TestSuite((
+#         doctest.DocFileSuite(*doctest_files, **kwargs)))
diff --git a/libs/bs4/tests/test_html5lib.py b/libs/bs4/tests/test_html5lib.py
new file mode 100644
index 000000000..96529b0b3
--- /dev/null
+++ b/libs/bs4/tests/test_html5lib.py
@@ -0,0 +1,170 @@
+"""Tests to ensure that the html5lib tree builder generates good trees."""
+
+import warnings
+
+try:
+    from bs4.builder import HTML5TreeBuilder
+    HTML5LIB_PRESENT = True
+except ImportError as e:
+    HTML5LIB_PRESENT = False
+from bs4.element import SoupStrainer
+from bs4.testing import (
+    HTML5TreeBuilderSmokeTest,
+    SoupTest,
+    skipIf,
+)
+
+@skipIf(
+    not HTML5LIB_PRESENT,
+    "html5lib seems not to be present, not testing its tree builder.")
+class HTML5LibBuilderSmokeTest(SoupTest, HTML5TreeBuilderSmokeTest):
+    """See ``HTML5TreeBuilderSmokeTest``."""
+
+    @property
+    def default_builder(self):
+        return HTML5TreeBuilder
+
+    def test_soupstrainer(self):
+        # The html5lib tree builder does not support SoupStrainers.
+        strainer = SoupStrainer("b")
+        markup = "<p>A <b>bold</b> statement.</p>"
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup(markup, parse_only=strainer)
+        self.assertEqual(
+            soup.decode(), self.document_for(markup))
+
+        self.assertTrue(
+            "the html5lib tree builder doesn't support parse_only" in
+            str(w[0].message))
+
+    def test_correctly_nested_tables(self):
+        """html5lib inserts <tbody> tags where other parsers don't."""
+        markup = ('<table id="1">'
+                  '<tr>'
+                  "<td>Here's another table:"
+                  '<table id="2">'
+                  '<tr><td>foo</td></tr>'
+                  '</table></td>')
+
+        self.assertSoupEquals(
+            markup,
+            '<table id="1"><tbody><tr><td>Here\'s another table:'
+            '<table id="2"><tbody><tr><td>foo</td></tr></tbody></table>'
+            '</td></tr></tbody></table>')
+
+        self.assertSoupEquals(
+            "<table><thead><tr><td>Foo</td></tr></thead>"
+            "<tbody><tr><td>Bar</td></tr></tbody>"
+            "<tfoot><tr><td>Baz</td></tr></tfoot></table>")
+
+    def test_xml_declaration_followed_by_doctype(self):
+        markup = '''<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE html>
+<html>
+  <head>
+  </head>
+  <body>
+   <p>foo</p>
+  </body>
+</html>'''
+        soup = self.soup(markup)
+        # Verify that we can reach the <p> tag; this means the tree is connected.
+        self.assertEqual(b"<p>foo</p>", soup.p.encode())
+
+    def test_reparented_markup(self):
+        markup = '<p><em>foo</p>\n<p>bar<a></a></em></p>'
+        soup = self.soup(markup)
+        self.assertEqual("<body><p><em>foo</em></p><em>\n</em><p><em>bar<a></a></em></p></body>", soup.body.decode())
+        self.assertEqual(2, len(soup.find_all('p')))
+
+
+    def test_reparented_markup_ends_with_whitespace(self):
+        markup = '<p><em>foo</p>\n<p>bar<a></a></em></p>\n'
+        soup = self.soup(markup)
+        self.assertEqual("<body><p><em>foo</em></p><em>\n</em><p><em>bar<a></a></em></p>\n</body>", soup.body.decode())
+        self.assertEqual(2, len(soup.find_all('p')))
+
+    def test_reparented_markup_containing_identical_whitespace_nodes(self):
+        """Verify that we keep the two whitespace nodes in this
+        document distinct when reparenting the adjacent <tbody> tags.
+        """
+        markup = '<table> <tbody><tbody><ims></tbody> </table>'
+        soup = self.soup(markup)
+        space1, space2 = soup.find_all(string=' ')
+        tbody1, tbody2 = soup.find_all('tbody')
+        assert space1.next_element is tbody1
+        assert tbody2.next_element is space2
+
+    def test_reparented_markup_containing_children(self):
+        markup = '<div><a>aftermath<p><noscript>target</noscript>aftermath</a></p></div>'
+        soup = self.soup(markup)
+        noscript = soup.noscript
+        self.assertEqual("target", noscript.next_element)
+        target = soup.find(string='target')
+
+        # The 'aftermath' string was duplicated; we want the second one.
+        final_aftermath = soup.find_all(string='aftermath')[-1]
+
+        # The <noscript> tag was moved beneath a copy of the <a> tag,
+        # but the 'target' string within is still connected to the
+        # (second) 'aftermath' string.
+        self.assertEqual(final_aftermath, target.next_element)
+        self.assertEqual(target, final_aftermath.previous_element)
+        
+    def test_processing_instruction(self):
+        """Processing instructions become comments."""
+        markup = b"""<?PITarget PIContent?>"""
+        soup = self.soup(markup)
+        assert str(soup).startswith("<!--?PITarget PIContent?-->")
+
+    def test_cloned_multivalue_node(self):
+        markup = b"""<a class="my_class"><p></a>"""
+        soup = self.soup(markup)
+        a1, a2 = soup.find_all('a')
+        self.assertEqual(a1, a2)
+        assert a1 is not a2
+
+    def test_foster_parenting(self):
+        markup = b"""<table><td></tbody>A"""
+        soup = self.soup(markup)
+        self.assertEqual("<body>A<table><tbody><tr><td></td></tr></tbody></table></body>", soup.body.decode())
+
+    def test_extraction(self):
+        """
+        Test that extraction does not destroy the tree.
+
+        https://bugs.launchpad.net/beautifulsoup/+bug/1782928
+        """
+
+        markup = """
+<html><head></head>
+<style>
+</style><script></script><body><p>hello</p></body></html>
+"""
+        soup = self.soup(markup)
+        [s.extract() for s in soup('script')]
+        [s.extract() for s in soup('style')]
+
+        self.assertEqual(len(soup.find_all("p")), 1)
+
+    def test_empty_comment(self):
+        """
+        Test that empty comment does not break structure.
+
+        https://bugs.launchpad.net/beautifulsoup/+bug/1806598
+        """
+
+        markup = """
+<html>
+<body>
+<form>
+<!----><input type="text">
+</form>
+</body>
+</html>
+"""
+        soup = self.soup(markup)
+        inputs = []
+        for form in soup.find_all('form'):
+            inputs.extend(form.find_all('input'))
+        self.assertEqual(len(inputs), 1)
diff --git a/libs/bs4/tests/test_htmlparser.py b/libs/bs4/tests/test_htmlparser.py
new file mode 100644
index 000000000..790489aa1
--- /dev/null
+++ b/libs/bs4/tests/test_htmlparser.py
@@ -0,0 +1,47 @@
+"""Tests to ensure that the html.parser tree builder generates good
+trees."""
+
+from pdb import set_trace
+import pickle
+from bs4.testing import SoupTest, HTMLTreeBuilderSmokeTest
+from bs4.builder import HTMLParserTreeBuilder
+from bs4.builder._htmlparser import BeautifulSoupHTMLParser
+
+class HTMLParserTreeBuilderSmokeTest(SoupTest, HTMLTreeBuilderSmokeTest):
+
+    default_builder = HTMLParserTreeBuilder
+
+    def test_namespaced_system_doctype(self):
+        # html.parser can't handle namespaced doctypes, so skip this one.
+        pass
+
+    def test_namespaced_public_doctype(self):
+        # html.parser can't handle namespaced doctypes, so skip this one.
+        pass
+
+    def test_builder_is_pickled(self):
+        """Unlike most tree builders, HTMLParserTreeBuilder and will
+        be restored after pickling.
+        """
+        tree = self.soup("<a><b>foo</a>")
+        dumped = pickle.dumps(tree, 2)
+        loaded = pickle.loads(dumped)
+        self.assertTrue(isinstance(loaded.builder, type(tree.builder)))
+
+    def test_redundant_empty_element_closing_tags(self):
+        self.assertSoupEquals('<br></br><br></br><br></br>', "<br/><br/><br/>")
+        self.assertSoupEquals('</br></br></br>', "")
+
+    def test_empty_element(self):
+        # This verifies that any buffered data present when the parser
+        # finishes working is handled.
+        self.assertSoupEquals("foo &# bar", "foo &amp;# bar")
+
+
+class TestHTMLParserSubclass(SoupTest):
+    def test_error(self):
+        """Verify that our HTMLParser subclass implements error() in a way
+        that doesn't cause a crash.
+        """
+        parser = BeautifulSoupHTMLParser()
+        parser.error("don't crash")
diff --git a/libs/bs4/tests/test_lxml.py b/libs/bs4/tests/test_lxml.py
new file mode 100644
index 000000000..29da71149
--- /dev/null
+++ b/libs/bs4/tests/test_lxml.py
@@ -0,0 +1,100 @@
+"""Tests to ensure that the lxml tree builder generates good trees."""
+
+import re
+import warnings
+
+try:
+    import lxml.etree
+    LXML_PRESENT = True
+    LXML_VERSION = lxml.etree.LXML_VERSION
+except ImportError as e:
+    LXML_PRESENT = False
+    LXML_VERSION = (0,)
+
+if LXML_PRESENT:
+    from bs4.builder import LXMLTreeBuilder, LXMLTreeBuilderForXML
+
+from bs4 import (
+    BeautifulSoup,
+    BeautifulStoneSoup,
+    )
+from bs4.element import Comment, Doctype, SoupStrainer
+from bs4.testing import skipIf
+from bs4.tests import test_htmlparser
+from bs4.testing import (
+    HTMLTreeBuilderSmokeTest,
+    XMLTreeBuilderSmokeTest,
+    SoupTest,
+    skipIf,
+)
+
+@skipIf(
+    not LXML_PRESENT,
+    "lxml seems not to be present, not testing its tree builder.")
+class LXMLTreeBuilderSmokeTest(SoupTest, HTMLTreeBuilderSmokeTest):
+    """See ``HTMLTreeBuilderSmokeTest``."""
+
+    @property
+    def default_builder(self):
+        return LXMLTreeBuilder
+
+    def test_out_of_range_entity(self):
+        self.assertSoupEquals(
+            "<p>foo&#10000000000000;bar</p>", "<p>foobar</p>")
+        self.assertSoupEquals(
+            "<p>foo&#x10000000000000;bar</p>", "<p>foobar</p>")
+        self.assertSoupEquals(
+            "<p>foo&#1000000000;bar</p>", "<p>foobar</p>")
+
+    def test_entities_in_foreign_document_encoding(self):
+        # We can't implement this case correctly because by the time we
+        # hear about markup like "&#147;", it's been (incorrectly) converted into
+        # a string like u'\x93'
+        pass
+        
+    # In lxml < 2.3.5, an empty doctype causes a segfault. Skip this
+    # test if an old version of lxml is installed.
+
+    @skipIf(
+        not LXML_PRESENT or LXML_VERSION < (2,3,5,0),
+        "Skipping doctype test for old version of lxml to avoid segfault.")
+    def test_empty_doctype(self):
+        soup = self.soup("<!DOCTYPE>")
+        doctype = soup.contents[0]
+        self.assertEqual("", doctype.strip())
+
+    def test_beautifulstonesoup_is_xml_parser(self):
+        # Make sure that the deprecated BSS class uses an xml builder
+        # if one is installed.
+        with warnings.catch_warnings(record=True) as w:
+            soup = BeautifulStoneSoup("<b />")
+        self.assertEqual("<b/>", str(soup.b))
+        self.assertTrue("BeautifulStoneSoup class is deprecated" in str(w[0].message))
+
+@skipIf(
+    not LXML_PRESENT,
+    "lxml seems not to be present, not testing its XML tree builder.")
+class LXMLXMLTreeBuilderSmokeTest(SoupTest, XMLTreeBuilderSmokeTest):
+    """See ``HTMLTreeBuilderSmokeTest``."""
+
+    @property
+    def default_builder(self):
+        return LXMLTreeBuilderForXML
+
+    def test_namespace_indexing(self):
+        # We should not track un-prefixed namespaces as we can only hold one
+        # and it will be recognized as the default namespace by soupsieve,
+        # which may be confusing in some situations. When no namespace is provided
+        # for a selector, the default namespace (if defined) is assumed.
+
+        soup = self.soup(
+            '<?xml version="1.1"?>\n'
+            '<root>'
+            '<tag xmlns="http://unprefixed-namespace.com">content</tag>'
+            '<prefix:tag xmlns:prefix="http://prefixed-namespace.com">content</tag>'
+            '</root>'
+        )
+        self.assertEqual(
+            soup._namespaces,
+            {'xml': 'http://www.w3.org/XML/1998/namespace', 'prefix': 'http://prefixed-namespace.com'}
+        )
diff --git a/libs/bs4/tests/test_soup.py b/libs/bs4/tests/test_soup.py
new file mode 100644
index 000000000..1eda9484b
--- /dev/null
+++ b/libs/bs4/tests/test_soup.py
@@ -0,0 +1,567 @@
+# -*- coding: utf-8 -*-
+"""Tests of Beautiful Soup as a whole."""
+
+from pdb import set_trace
+import logging
+import unittest
+import sys
+import tempfile
+
+from bs4 import (
+    BeautifulSoup,
+    BeautifulStoneSoup,
+)
+from bs4.element import (
+    CharsetMetaAttributeValue,
+    ContentMetaAttributeValue,
+    SoupStrainer,
+    NamespacedAttribute,
+    )
+import bs4.dammit
+from bs4.dammit import (
+    EntitySubstitution,
+    UnicodeDammit,
+    EncodingDetector,
+)
+from bs4.testing import (
+    default_builder,
+    SoupTest,
+    skipIf,
+)
+import warnings
+
+try:
+    from bs4.builder import LXMLTreeBuilder, LXMLTreeBuilderForXML
+    LXML_PRESENT = True
+except ImportError as e:
+    LXML_PRESENT = False
+
+PYTHON_3_PRE_3_2 = (sys.version_info[0] == 3 and sys.version_info < (3,2))
+
+class TestConstructor(SoupTest):
+
+    def test_short_unicode_input(self):
+        data = "<h1>éé</h1>"
+        soup = self.soup(data)
+        self.assertEqual("éé", soup.h1.string)
+
+    def test_embedded_null(self):
+        data = "<h1>foo\0bar</h1>"
+        soup = self.soup(data)
+        self.assertEqual("foo\0bar", soup.h1.string)
+
+    def test_exclude_encodings(self):
+        utf8_data = "Räksmörgås".encode("utf-8")
+        soup = self.soup(utf8_data, exclude_encodings=["utf-8"])
+        self.assertEqual("windows-1252", soup.original_encoding)
+
+    def test_custom_builder_class(self):
+        # Verify that you can pass in a custom Builder class and
+        # it'll be instantiated with the appropriate keyword arguments.
+        class Mock(object):
+            def __init__(self, **kwargs):
+                self.called_with = kwargs
+                self.is_xml = True
+            def initialize_soup(self, soup):
+                pass
+            def prepare_markup(self, *args, **kwargs):
+                return ''
+                
+        kwargs = dict(
+            var="value",
+            # This is a deprecated BS3-era keyword argument, which
+            # will be stripped out.
+            convertEntities=True,
+        )
+        with warnings.catch_warnings(record=True):
+            soup = BeautifulSoup('', builder=Mock, **kwargs)
+        assert isinstance(soup.builder, Mock)
+        self.assertEqual(dict(var="value"), soup.builder.called_with)
+
+        # You can also instantiate the TreeBuilder yourself. In this
+        # case, that specific object is used and any keyword arguments
+        # to the BeautifulSoup constructor are ignored.
+        builder = Mock(**kwargs)
+        with warnings.catch_warnings(record=True) as w:
+            soup = BeautifulSoup(
+                '', builder=builder, ignored_value=True,
+            )
+        msg = str(w[0].message)
+        assert msg.startswith("Keyword arguments to the BeautifulSoup constructor will be ignored.")
+        self.assertEqual(builder, soup.builder)
+        self.assertEqual(kwargs, builder.called_with)
+
+    def test_cdata_list_attributes(self):
+        # Most attribute values are represented as scalars, but the
+        # HTML standard says that some attributes, like 'class' have
+        # space-separated lists as values.
+        markup = '<a id=" an id " class=" a class "></a>'
+        soup = self.soup(markup)
+
+        # Note that the spaces are stripped for 'class' but not for 'id'.
+        a = soup.a
+        self.assertEqual(" an id ", a['id'])
+        self.assertEqual(["a", "class"], a['class'])
+
+        # TreeBuilder takes an argument called 'mutli_valued_attributes'  which lets
+        # you customize or disable this. As always, you can customize the TreeBuilder
+        # by passing in a keyword argument to the BeautifulSoup constructor.
+        soup = self.soup(markup, builder=default_builder, multi_valued_attributes=None)
+        self.assertEqual(" a class ", soup.a['class'])
+
+        # Here are two ways of saying that `id` is a multi-valued
+        # attribute in this context, but 'class' is not.
+        for switcheroo in ({'*': 'id'}, {'a': 'id'}):
+            with warnings.catch_warnings(record=True) as w:
+                # This will create a warning about not explicitly
+                # specifying a parser, but we'll ignore it.
+                soup = self.soup(markup, builder=None, multi_valued_attributes=switcheroo)
+            a = soup.a
+            self.assertEqual(["an", "id"], a['id'])
+            self.assertEqual(" a class ", a['class'])
+
+        
+class TestWarnings(SoupTest):
+
+    def _no_parser_specified(self, s, is_there=True):
+        v = s.startswith(BeautifulSoup.NO_PARSER_SPECIFIED_WARNING[:80])
+        self.assertTrue(v)
+
+    def test_warning_if_no_parser_specified(self):
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup("<a><b></b></a>")
+        msg = str(w[0].message)
+        self._assert_no_parser_specified(msg)
+
+    def test_warning_if_parser_specified_too_vague(self):
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup("<a><b></b></a>", "html")
+        msg = str(w[0].message)
+        self._assert_no_parser_specified(msg)
+
+    def test_no_warning_if_explicit_parser_specified(self):
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup("<a><b></b></a>", "html.parser")
+        self.assertEqual([], w)
+
+    def test_parseOnlyThese_renamed_to_parse_only(self):
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup("<a><b></b></a>", parseOnlyThese=SoupStrainer("b"))
+        msg = str(w[0].message)
+        self.assertTrue("parseOnlyThese" in msg)
+        self.assertTrue("parse_only" in msg)
+        self.assertEqual(b"<b></b>", soup.encode())
+
+    def test_fromEncoding_renamed_to_from_encoding(self):
+        with warnings.catch_warnings(record=True) as w:
+            utf8 = b"\xc3\xa9"
+            soup = self.soup(utf8, fromEncoding="utf8")
+        msg = str(w[0].message)
+        self.assertTrue("fromEncoding" in msg)
+        self.assertTrue("from_encoding" in msg)
+        self.assertEqual("utf8", soup.original_encoding)
+
+    def test_unrecognized_keyword_argument(self):
+        self.assertRaises(
+            TypeError, self.soup, "<a>", no_such_argument=True)
+
+class TestWarnings(SoupTest):
+
+    def test_disk_file_warning(self):
+        filehandle = tempfile.NamedTemporaryFile()
+        filename = filehandle.name
+        try:
+            with warnings.catch_warnings(record=True) as w:
+                soup = self.soup(filename)
+            msg = str(w[0].message)
+            self.assertTrue("looks like a filename" in msg)
+        finally:
+            filehandle.close()
+
+        # The file no longer exists, so Beautiful Soup will no longer issue the warning.
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup(filename)
+        self.assertEqual(0, len(w))
+
+    def test_url_warning_with_bytes_url(self):
+        with warnings.catch_warnings(record=True) as warning_list:
+            soup = self.soup(b"http://www.crummybytes.com/")
+        # Be aware this isn't the only warning that can be raised during
+        # execution..
+        self.assertTrue(any("looks like a URL" in str(w.message) 
+            for w in warning_list))
+
+    def test_url_warning_with_unicode_url(self):
+        with warnings.catch_warnings(record=True) as warning_list:
+            # note - this url must differ from the bytes one otherwise
+            # python's warnings system swallows the second warning
+            soup = self.soup("http://www.crummyunicode.com/")
+        self.assertTrue(any("looks like a URL" in str(w.message) 
+            for w in warning_list))
+
+    def test_url_warning_with_bytes_and_space(self):
+        with warnings.catch_warnings(record=True) as warning_list:
+            soup = self.soup(b"http://www.crummybytes.com/ is great")
+        self.assertFalse(any("looks like a URL" in str(w.message) 
+            for w in warning_list))
+
+    def test_url_warning_with_unicode_and_space(self):
+        with warnings.catch_warnings(record=True) as warning_list:
+            soup = self.soup("http://www.crummyuncode.com/ is great")
+        self.assertFalse(any("looks like a URL" in str(w.message) 
+            for w in warning_list))
+
+
+class TestSelectiveParsing(SoupTest):
+
+    def test_parse_with_soupstrainer(self):
+        markup = "No<b>Yes</b><a>No<b>Yes <c>Yes</c></b>"
+        strainer = SoupStrainer("b")
+        soup = self.soup(markup, parse_only=strainer)
+        self.assertEqual(soup.encode(), b"<b>Yes</b><b>Yes <c>Yes</c></b>")
+
+
+class TestEntitySubstitution(unittest.TestCase):
+    """Standalone tests of the EntitySubstitution class."""
+    def setUp(self):
+        self.sub = EntitySubstitution
+
+    def test_simple_html_substitution(self):
+        # Unicode characters corresponding to named HTML entites
+        # are substituted, and no others.
+        s = "foo\u2200\N{SNOWMAN}\u00f5bar"
+        self.assertEqual(self.sub.substitute_html(s),
+                          "foo&forall;\N{SNOWMAN}&otilde;bar")
+
+    def test_smart_quote_substitution(self):
+        # MS smart quotes are a common source of frustration, so we
+        # give them a special test.
+        quotes = b"\x91\x92foo\x93\x94"
+        dammit = UnicodeDammit(quotes)
+        self.assertEqual(self.sub.substitute_html(dammit.markup),
+                          "&lsquo;&rsquo;foo&ldquo;&rdquo;")
+
+    def test_xml_converstion_includes_no_quotes_if_make_quoted_attribute_is_false(self):
+        s = 'Welcome to "my bar"'
+        self.assertEqual(self.sub.substitute_xml(s, False), s)
+
+    def test_xml_attribute_quoting_normally_uses_double_quotes(self):
+        self.assertEqual(self.sub.substitute_xml("Welcome", True),
+                          '"Welcome"')
+        self.assertEqual(self.sub.substitute_xml("Bob's Bar", True),
+                          '"Bob\'s Bar"')
+
+    def test_xml_attribute_quoting_uses_single_quotes_when_value_contains_double_quotes(self):
+        s = 'Welcome to "my bar"'
+        self.assertEqual(self.sub.substitute_xml(s, True),
+                          "'Welcome to \"my bar\"'")
+
+    def test_xml_attribute_quoting_escapes_single_quotes_when_value_contains_both_single_and_double_quotes(self):
+        s = 'Welcome to "Bob\'s Bar"'
+        self.assertEqual(
+            self.sub.substitute_xml(s, True),
+            '"Welcome to &quot;Bob\'s Bar&quot;"')
+
+    def test_xml_quotes_arent_escaped_when_value_is_not_being_quoted(self):
+        quoted = 'Welcome to "Bob\'s Bar"'
+        self.assertEqual(self.sub.substitute_xml(quoted), quoted)
+
+    def test_xml_quoting_handles_angle_brackets(self):
+        self.assertEqual(
+            self.sub.substitute_xml("foo<bar>"),
+            "foo&lt;bar&gt;")
+
+    def test_xml_quoting_handles_ampersands(self):
+        self.assertEqual(self.sub.substitute_xml("AT&T"), "AT&amp;T")
+
+    def test_xml_quoting_including_ampersands_when_they_are_part_of_an_entity(self):
+        self.assertEqual(
+            self.sub.substitute_xml("&Aacute;T&T"),
+            "&amp;Aacute;T&amp;T")
+
+    def test_xml_quoting_ignoring_ampersands_when_they_are_part_of_an_entity(self):
+        self.assertEqual(
+            self.sub.substitute_xml_containing_entities("&Aacute;T&T"),
+            "&Aacute;T&amp;T")
+       
+    def test_quotes_not_html_substituted(self):
+        """There's no need to do this except inside attribute values."""
+        text = 'Bob\'s "bar"'
+        self.assertEqual(self.sub.substitute_html(text), text)
+
+
+class TestEncodingConversion(SoupTest):
+    # Test Beautiful Soup's ability to decode and encode from various
+    # encodings.
+
+    def setUp(self):
+        super(TestEncodingConversion, self).setUp()
+        self.unicode_data = '<html><head><meta charset="utf-8"/></head><body><foo>Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!</foo></body></html>'
+        self.utf8_data = self.unicode_data.encode("utf-8")
+        # Just so you know what it looks like.
+        self.assertEqual(
+            self.utf8_data,
+            b'<html><head><meta charset="utf-8"/></head><body><foo>Sacr\xc3\xa9 bleu!</foo></body></html>')
+
+    def test_ascii_in_unicode_out(self):
+        # ASCII input is converted to Unicode. The original_encoding
+        # attribute is set to 'utf-8', a superset of ASCII.
+        chardet = bs4.dammit.chardet_dammit
+        logging.disable(logging.WARNING)
+        try:
+            def noop(str):
+                return None
+            # Disable chardet, which will realize that the ASCII is ASCII.
+            bs4.dammit.chardet_dammit = noop
+            ascii = b"<foo>a</foo>"
+            soup_from_ascii = self.soup(ascii)
+            unicode_output = soup_from_ascii.decode()
+            self.assertTrue(isinstance(unicode_output, str))
+            self.assertEqual(unicode_output, self.document_for(ascii.decode()))
+            self.assertEqual(soup_from_ascii.original_encoding.lower(), "utf-8")
+        finally:
+            logging.disable(logging.NOTSET)
+            bs4.dammit.chardet_dammit = chardet
+
+    def test_unicode_in_unicode_out(self):
+        # Unicode input is left alone. The original_encoding attribute
+        # is not set.
+        soup_from_unicode = self.soup(self.unicode_data)
+        self.assertEqual(soup_from_unicode.decode(), self.unicode_data)
+        self.assertEqual(soup_from_unicode.foo.string, 'Sacr\xe9 bleu!')
+        self.assertEqual(soup_from_unicode.original_encoding, None)
+
+    def test_utf8_in_unicode_out(self):
+        # UTF-8 input is converted to Unicode. The original_encoding
+        # attribute is set.
+        soup_from_utf8 = self.soup(self.utf8_data)
+        self.assertEqual(soup_from_utf8.decode(), self.unicode_data)
+        self.assertEqual(soup_from_utf8.foo.string, 'Sacr\xe9 bleu!')
+
+    def test_utf8_out(self):
+        # The internal data structures can be encoded as UTF-8.
+        soup_from_unicode = self.soup(self.unicode_data)
+        self.assertEqual(soup_from_unicode.encode('utf-8'), self.utf8_data)
+
+    @skipIf(
+        PYTHON_3_PRE_3_2,
+        "Bad HTMLParser detected; skipping test of non-ASCII characters in attribute name.")
+    def test_attribute_name_containing_unicode_characters(self):
+        markup = '<div><a \N{SNOWMAN}="snowman"></a></div>'
+        self.assertEqual(self.soup(markup).div.encode("utf8"), markup.encode("utf8"))
+
+class TestUnicodeDammit(unittest.TestCase):
+    """Standalone tests of UnicodeDammit."""
+
+    def test_unicode_input(self):
+        markup = "I'm already Unicode! \N{SNOWMAN}"
+        dammit = UnicodeDammit(markup)
+        self.assertEqual(dammit.unicode_markup, markup)
+
+    def test_smart_quotes_to_unicode(self):
+        markup = b"<foo>\x91\x92\x93\x94</foo>"
+        dammit = UnicodeDammit(markup)
+        self.assertEqual(
+            dammit.unicode_markup, "<foo>\u2018\u2019\u201c\u201d</foo>")
+
+    def test_smart_quotes_to_xml_entities(self):
+        markup = b"<foo>\x91\x92\x93\x94</foo>"
+        dammit = UnicodeDammit(markup, smart_quotes_to="xml")
+        self.assertEqual(
+            dammit.unicode_markup, "<foo>&#x2018;&#x2019;&#x201C;&#x201D;</foo>")
+
+    def test_smart_quotes_to_html_entities(self):
+        markup = b"<foo>\x91\x92\x93\x94</foo>"
+        dammit = UnicodeDammit(markup, smart_quotes_to="html")
+        self.assertEqual(
+            dammit.unicode_markup, "<foo>&lsquo;&rsquo;&ldquo;&rdquo;</foo>")
+
+    def test_smart_quotes_to_ascii(self):
+        markup = b"<foo>\x91\x92\x93\x94</foo>"
+        dammit = UnicodeDammit(markup, smart_quotes_to="ascii")
+        self.assertEqual(
+            dammit.unicode_markup, """<foo>''""</foo>""")
+
+    def test_detect_utf8(self):
+        utf8 = b"Sacr\xc3\xa9 bleu! \xe2\x98\x83"
+        dammit = UnicodeDammit(utf8)
+        self.assertEqual(dammit.original_encoding.lower(), 'utf-8')
+        self.assertEqual(dammit.unicode_markup, 'Sacr\xe9 bleu! \N{SNOWMAN}')
+
+
+    def test_convert_hebrew(self):
+        hebrew = b"\xed\xe5\xec\xf9"
+        dammit = UnicodeDammit(hebrew, ["iso-8859-8"])
+        self.assertEqual(dammit.original_encoding.lower(), 'iso-8859-8')
+        self.assertEqual(dammit.unicode_markup, '\u05dd\u05d5\u05dc\u05e9')
+
+    def test_dont_see_smart_quotes_where_there_are_none(self):
+        utf_8 = b"\343\202\261\343\203\274\343\202\277\343\202\244 Watch"
+        dammit = UnicodeDammit(utf_8)
+        self.assertEqual(dammit.original_encoding.lower(), 'utf-8')
+        self.assertEqual(dammit.unicode_markup.encode("utf-8"), utf_8)
+
+    def test_ignore_inappropriate_codecs(self):
+        utf8_data = "Räksmörgås".encode("utf-8")
+        dammit = UnicodeDammit(utf8_data, ["iso-8859-8"])
+        self.assertEqual(dammit.original_encoding.lower(), 'utf-8')
+
+    def test_ignore_invalid_codecs(self):
+        utf8_data = "Räksmörgås".encode("utf-8")
+        for bad_encoding in ['.utf8', '...', 'utF---16.!']:
+            dammit = UnicodeDammit(utf8_data, [bad_encoding])
+            self.assertEqual(dammit.original_encoding.lower(), 'utf-8')
+
+    def test_exclude_encodings(self):
+        # This is UTF-8.
+        utf8_data = "Räksmörgås".encode("utf-8")
+
+        # But if we exclude UTF-8 from consideration, the guess is
+        # Windows-1252.
+        dammit = UnicodeDammit(utf8_data, exclude_encodings=["utf-8"])
+        self.assertEqual(dammit.original_encoding.lower(), 'windows-1252')
+
+        # And if we exclude that, there is no valid guess at all.
+        dammit = UnicodeDammit(
+            utf8_data, exclude_encodings=["utf-8", "windows-1252"])
+        self.assertEqual(dammit.original_encoding, None)
+
+    def test_encoding_detector_replaces_junk_in_encoding_name_with_replacement_character(self):
+        detected = EncodingDetector(
+            b'<?xml version="1.0" encoding="UTF-\xdb" ?>')
+        encodings = list(detected.encodings)
+        assert 'utf-\N{REPLACEMENT CHARACTER}' in encodings
+
+    def test_detect_html5_style_meta_tag(self):
+
+        for data in (
+            b'<html><meta charset="euc-jp" /></html>',
+            b"<html><meta charset='euc-jp' /></html>",
+            b"<html><meta charset=euc-jp /></html>",
+            b"<html><meta charset=euc-jp/></html>"):
+            dammit = UnicodeDammit(data, is_html=True)
+            self.assertEqual(
+                "euc-jp", dammit.original_encoding)
+
+    def test_last_ditch_entity_replacement(self):
+        # This is a UTF-8 document that contains bytestrings
+        # completely incompatible with UTF-8 (ie. encoded with some other
+        # encoding).
+        #
+        # Since there is no consistent encoding for the document,
+        # Unicode, Dammit will eventually encode the document as UTF-8
+        # and encode the incompatible characters as REPLACEMENT
+        # CHARACTER.
+        #
+        # If chardet is installed, it will detect that the document
+        # can be converted into ISO-8859-1 without errors. This happens
+        # to be the wrong encoding, but it is a consistent encoding, so the
+        # code we're testing here won't run.
+        #
+        # So we temporarily disable chardet if it's present.
+        doc = b"""\357\273\277<?xml version="1.0" encoding="UTF-8"?>
+<html><b>\330\250\330\252\330\261</b>
+<i>\310\322\321\220\312\321\355\344</i></html>"""
+        chardet = bs4.dammit.chardet_dammit
+        logging.disable(logging.WARNING)
+        try:
+            def noop(str):
+                return None
+            bs4.dammit.chardet_dammit = noop
+            dammit = UnicodeDammit(doc)
+            self.assertEqual(True, dammit.contains_replacement_characters)
+            self.assertTrue("\ufffd" in dammit.unicode_markup)
+
+            soup = BeautifulSoup(doc, "html.parser")
+            self.assertTrue(soup.contains_replacement_characters)
+        finally:
+            logging.disable(logging.NOTSET)
+            bs4.dammit.chardet_dammit = chardet
+
+    def test_byte_order_mark_removed(self):
+        # A document written in UTF-16LE will have its byte order marker stripped.
+        data = b'\xff\xfe<\x00a\x00>\x00\xe1\x00\xe9\x00<\x00/\x00a\x00>\x00'
+        dammit = UnicodeDammit(data)
+        self.assertEqual("<a>áé</a>", dammit.unicode_markup)
+        self.assertEqual("utf-16le", dammit.original_encoding)
+
+    def test_detwingle(self):
+        # Here's a UTF8 document.
+        utf8 = ("\N{SNOWMAN}" * 3).encode("utf8")
+
+        # Here's a Windows-1252 document.
+        windows_1252 = (
+            "\N{LEFT DOUBLE QUOTATION MARK}Hi, I like Windows!"
+            "\N{RIGHT DOUBLE QUOTATION MARK}").encode("windows_1252")
+
+        # Through some unholy alchemy, they've been stuck together.
+        doc = utf8 + windows_1252 + utf8
+
+        # The document can't be turned into UTF-8:
+        self.assertRaises(UnicodeDecodeError, doc.decode, "utf8")
+
+        # Unicode, Dammit thinks the whole document is Windows-1252,
+        # and decodes it into "☃☃☃“Hi, I like Windows!”☃☃☃"
+
+        # But if we run it through fix_embedded_windows_1252, it's fixed:
+
+        fixed = UnicodeDammit.detwingle(doc)
+        self.assertEqual(
+            "☃☃☃“Hi, I like Windows!”☃☃☃", fixed.decode("utf8"))
+
+    def test_detwingle_ignores_multibyte_characters(self):
+        # Each of these characters has a UTF-8 representation ending
+        # in \x93. \x93 is a smart quote if interpreted as
+        # Windows-1252. But our code knows to skip over multibyte
+        # UTF-8 characters, so they'll survive the process unscathed.
+        for tricky_unicode_char in (
+            "\N{LATIN SMALL LIGATURE OE}", # 2-byte char '\xc5\x93'
+            "\N{LATIN SUBSCRIPT SMALL LETTER X}", # 3-byte char '\xe2\x82\x93'
+            "\xf0\x90\x90\x93", # This is a CJK character, not sure which one.
+            ):
+            input = tricky_unicode_char.encode("utf8")
+            self.assertTrue(input.endswith(b'\x93'))
+            output = UnicodeDammit.detwingle(input)
+            self.assertEqual(output, input)
+
+class TestNamedspacedAttribute(SoupTest):
+
+    def test_name_may_be_none(self):
+        a = NamespacedAttribute("xmlns", None)
+        self.assertEqual(a, "xmlns")
+
+    def test_attribute_is_equivalent_to_colon_separated_string(self):
+        a = NamespacedAttribute("a", "b")
+        self.assertEqual("a:b", a)
+
+    def test_attributes_are_equivalent_if_prefix_and_name_identical(self):
+        a = NamespacedAttribute("a", "b", "c")
+        b = NamespacedAttribute("a", "b", "c")
+        self.assertEqual(a, b)
+
+        # The actual namespace is not considered.
+        c = NamespacedAttribute("a", "b", None)
+        self.assertEqual(a, c)
+
+        # But name and prefix are important.
+        d = NamespacedAttribute("a", "z", "c")
+        self.assertNotEqual(a, d)
+
+        e = NamespacedAttribute("z", "b", "c")
+        self.assertNotEqual(a, e)
+
+
+class TestAttributeValueWithCharsetSubstitution(unittest.TestCase):
+
+    def test_content_meta_attribute_value(self):
+        value = CharsetMetaAttributeValue("euc-jp")
+        self.assertEqual("euc-jp", value)
+        self.assertEqual("euc-jp", value.original_value)
+        self.assertEqual("utf8", value.encode("utf8"))
+
+
+    def test_content_meta_attribute_value(self):
+        value = ContentMetaAttributeValue("text/html; charset=euc-jp")
+        self.assertEqual("text/html; charset=euc-jp", value)
+        self.assertEqual("text/html; charset=euc-jp", value.original_value)
+        self.assertEqual("text/html; charset=utf8", value.encode("utf8"))
diff --git a/libs/bs4/tests/test_tree.py b/libs/bs4/tests/test_tree.py
new file mode 100644
index 000000000..3b4beeb8f
--- /dev/null
+++ b/libs/bs4/tests/test_tree.py
@@ -0,0 +1,2205 @@
+# -*- coding: utf-8 -*-
+"""Tests for Beautiful Soup's tree traversal methods.
+
+The tree traversal methods are the main advantage of using Beautiful
+Soup over just using a parser.
+
+Different parsers will build different Beautiful Soup trees given the
+same markup, but all Beautiful Soup trees can be traversed with the
+methods tested here.
+"""
+
+from pdb import set_trace
+import copy
+import pickle
+import re
+import warnings
+from bs4 import BeautifulSoup
+from bs4.builder import (
+    builder_registry,
+    HTMLParserTreeBuilder,
+)
+from bs4.element import (
+    PY3K,
+    CData,
+    Comment,
+    Declaration,
+    Doctype,
+    Formatter,
+    NavigableString,
+    SoupStrainer,
+    Tag,
+)
+from bs4.testing import (
+    SoupTest,
+    skipIf,
+)
+
+XML_BUILDER_PRESENT = (builder_registry.lookup("xml") is not None)
+LXML_PRESENT = (builder_registry.lookup("lxml") is not None)
+
+class TreeTest(SoupTest):
+
+    def assertSelects(self, tags, should_match):
+        """Make sure that the given tags have the correct text.
+
+        This is used in tests that define a bunch of tags, each
+        containing a single string, and then select certain strings by
+        some mechanism.
+        """
+        self.assertEqual([tag.string for tag in tags], should_match)
+
+    def assertSelectsIDs(self, tags, should_match):
+        """Make sure that the given tags have the correct IDs.
+
+        This is used in tests that define a bunch of tags, each
+        containing a single string, and then select certain strings by
+        some mechanism.
+        """
+        self.assertEqual([tag['id'] for tag in tags], should_match)
+
+
+class TestFind(TreeTest):
+    """Basic tests of the find() method.
+
+    find() just calls find_all() with limit=1, so it's not tested all
+    that thouroughly here.
+    """
+
+    def test_find_tag(self):
+        soup = self.soup("<a>1</a><b>2</b><a>3</a><b>4</b>")
+        self.assertEqual(soup.find("b").string, "2")
+
+    def test_unicode_text_find(self):
+        soup = self.soup('<h1>Räksmörgås</h1>')
+        self.assertEqual(soup.find(string='Räksmörgås'), 'Räksmörgås')
+
+    def test_unicode_attribute_find(self):
+        soup = self.soup('<h1 id="Räksmörgås">here it is</h1>')
+        str(soup)
+        self.assertEqual("here it is", soup.find(id='Räksmörgås').text)
+
+
+    def test_find_everything(self):
+        """Test an optimization that finds all tags."""
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        self.assertEqual(2, len(soup.find_all()))
+
+    def test_find_everything_with_name(self):
+        """Test an optimization that finds all tags with a given name."""
+        soup = self.soup("<a>foo</a><b>bar</b><a>baz</a>")
+        self.assertEqual(2, len(soup.find_all('a')))
+
+class TestFindAll(TreeTest):
+    """Basic tests of the find_all() method."""
+
+    def test_find_all_text_nodes(self):
+        """You can search the tree for text nodes."""
+        soup = self.soup("<html>Foo<b>bar</b>\xbb</html>")
+        # Exact match.
+        self.assertEqual(soup.find_all(string="bar"), ["bar"])
+        self.assertEqual(soup.find_all(text="bar"), ["bar"])
+        # Match any of a number of strings.
+        self.assertEqual(
+            soup.find_all(text=["Foo", "bar"]), ["Foo", "bar"])
+        # Match a regular expression.
+        self.assertEqual(soup.find_all(text=re.compile('.*')),
+                         ["Foo", "bar", '\xbb'])
+        # Match anything.
+        self.assertEqual(soup.find_all(text=True),
+                         ["Foo", "bar", '\xbb'])
+
+    def test_find_all_limit(self):
+        """You can limit the number of items returned by find_all."""
+        soup = self.soup("<a>1</a><a>2</a><a>3</a><a>4</a><a>5</a>")
+        self.assertSelects(soup.find_all('a', limit=3), ["1", "2", "3"])
+        self.assertSelects(soup.find_all('a', limit=1), ["1"])
+        self.assertSelects(
+            soup.find_all('a', limit=10), ["1", "2", "3", "4", "5"])
+
+        # A limit of 0 means no limit.
+        self.assertSelects(
+            soup.find_all('a', limit=0), ["1", "2", "3", "4", "5"])
+
+    def test_calling_a_tag_is_calling_findall(self):
+        soup = self.soup("<a>1</a><b>2<a id='foo'>3</a></b>")
+        self.assertSelects(soup('a', limit=1), ["1"])
+        self.assertSelects(soup.b(id="foo"), ["3"])
+
+    def test_find_all_with_self_referential_data_structure_does_not_cause_infinite_recursion(self):
+        soup = self.soup("<a></a>")
+        # Create a self-referential list.
+        l = []
+        l.append(l)
+
+        # Without special code in _normalize_search_value, this would cause infinite
+        # recursion.
+        self.assertEqual([], soup.find_all(l))
+
+    def test_find_all_resultset(self):
+        """All find_all calls return a ResultSet"""
+        soup = self.soup("<a></a>")
+        result = soup.find_all("a")
+        self.assertTrue(hasattr(result, "source"))
+
+        result = soup.find_all(True)
+        self.assertTrue(hasattr(result, "source"))
+
+        result = soup.find_all(text="foo")
+        self.assertTrue(hasattr(result, "source"))
+
+
+class TestFindAllBasicNamespaces(TreeTest):
+
+    def test_find_by_namespaced_name(self):
+        soup = self.soup('<mathml:msqrt>4</mathml:msqrt><a svg:fill="red">')
+        self.assertEqual("4", soup.find("mathml:msqrt").string)
+        self.assertEqual("a", soup.find(attrs= { "svg:fill" : "red" }).name)
+
+
+class TestFindAllByName(TreeTest):
+    """Test ways of finding tags by tag name."""
+
+    def setUp(self):
+        super(TreeTest, self).setUp()
+        self.tree =  self.soup("""<a>First tag.</a>
+                                  <b>Second tag.</b>
+                                  <c>Third <a>Nested tag.</a> tag.</c>""")
+
+    def test_find_all_by_tag_name(self):
+        # Find all the <a> tags.
+        self.assertSelects(
+            self.tree.find_all('a'), ['First tag.', 'Nested tag.'])
+
+    def test_find_all_by_name_and_text(self):
+        self.assertSelects(
+            self.tree.find_all('a', text='First tag.'), ['First tag.'])
+
+        self.assertSelects(
+            self.tree.find_all('a', text=True), ['First tag.', 'Nested tag.'])
+
+        self.assertSelects(
+            self.tree.find_all('a', text=re.compile("tag")),
+            ['First tag.', 'Nested tag.'])
+
+
+    def test_find_all_on_non_root_element(self):
+        # You can call find_all on any node, not just the root.
+        self.assertSelects(self.tree.c.find_all('a'), ['Nested tag.'])
+
+    def test_calling_element_invokes_find_all(self):
+        self.assertSelects(self.tree('a'), ['First tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_strainer(self):
+        self.assertSelects(
+            self.tree.find_all(SoupStrainer('a')),
+            ['First tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_names(self):
+        self.assertSelects(
+            self.tree.find_all(['a', 'b']),
+            ['First tag.', 'Second tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_dict(self):
+        self.assertSelects(
+            self.tree.find_all({'a' : True, 'b' : True}),
+            ['First tag.', 'Second tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_re(self):
+        self.assertSelects(
+            self.tree.find_all(re.compile('^[ab]$')),
+            ['First tag.', 'Second tag.', 'Nested tag.'])
+
+    def test_find_all_with_tags_matching_method(self):
+        # You can define an oracle method that determines whether
+        # a tag matches the search.
+        def id_matches_name(tag):
+            return tag.name == tag.get('id')
+
+        tree = self.soup("""<a id="a">Match 1.</a>
+                            <a id="1">Does not match.</a>
+                            <b id="b">Match 2.</a>""")
+
+        self.assertSelects(
+            tree.find_all(id_matches_name), ["Match 1.", "Match 2."])
+
+    def test_find_with_multi_valued_attribute(self):
+        soup = self.soup(
+            "<div class='a b'>1</div><div class='a c'>2</div><div class='a d'>3</div>"
+        )
+        r1 = soup.find('div', 'a d');
+        r2 = soup.find('div', re.compile(r'a d'));
+        r3, r4 = soup.find_all('div', ['a b', 'a d']);
+        self.assertEqual('3', r1.string)
+        self.assertEqual('3', r2.string)
+        self.assertEqual('1', r3.string)
+        self.assertEqual('3', r4.string)
+
+        
+class TestFindAllByAttribute(TreeTest):
+
+    def test_find_all_by_attribute_name(self):
+        # You can pass in keyword arguments to find_all to search by
+        # attribute.
+        tree = self.soup("""
+                         <a id="first">Matching a.</a>
+                         <a id="second">
+                          Non-matching <b id="first">Matching b.</b>a.
+                         </a>""")
+        self.assertSelects(tree.find_all(id='first'),
+                           ["Matching a.", "Matching b."])
+
+    def test_find_all_by_utf8_attribute_value(self):
+        peace = "םולש".encode("utf8")
+        data = '<a title="םולש"></a>'.encode("utf8")
+        soup = self.soup(data)
+        self.assertEqual([soup.a], soup.find_all(title=peace))
+        self.assertEqual([soup.a], soup.find_all(title=peace.decode("utf8")))
+        self.assertEqual([soup.a], soup.find_all(title=[peace, "something else"]))
+
+    def test_find_all_by_attribute_dict(self):
+        # You can pass in a dictionary as the argument 'attrs'. This
+        # lets you search for attributes like 'name' (a fixed argument
+        # to find_all) and 'class' (a reserved word in Python.)
+        tree = self.soup("""
+                         <a name="name1" class="class1">Name match.</a>
+                         <a name="name2" class="class2">Class match.</a>
+                         <a name="name3" class="class3">Non-match.</a>
+                         <name1>A tag called 'name1'.</name1>
+                         """)
+
+        # This doesn't do what you want.
+        self.assertSelects(tree.find_all(name='name1'),
+                           ["A tag called 'name1'."])
+        # This does what you want.
+        self.assertSelects(tree.find_all(attrs={'name' : 'name1'}),
+                           ["Name match."])
+
+        self.assertSelects(tree.find_all(attrs={'class' : 'class2'}),
+                           ["Class match."])
+
+    def test_find_all_by_class(self):
+        tree = self.soup("""
+                         <a class="1">Class 1.</a>
+                         <a class="2">Class 2.</a>
+                         <b class="1">Class 1.</b>
+                         <c class="3 4">Class 3 and 4.</c>
+                         """)
+
+        # Passing in the class_ keyword argument will search against
+        # the 'class' attribute.
+        self.assertSelects(tree.find_all('a', class_='1'), ['Class 1.'])
+        self.assertSelects(tree.find_all('c', class_='3'), ['Class 3 and 4.'])
+        self.assertSelects(tree.find_all('c', class_='4'), ['Class 3 and 4.'])
+
+        # Passing in a string to 'attrs' will also search the CSS class.
+        self.assertSelects(tree.find_all('a', '1'), ['Class 1.'])
+        self.assertSelects(tree.find_all(attrs='1'), ['Class 1.', 'Class 1.'])
+        self.assertSelects(tree.find_all('c', '3'), ['Class 3 and 4.'])
+        self.assertSelects(tree.find_all('c', '4'), ['Class 3 and 4.'])
+
+    def test_find_by_class_when_multiple_classes_present(self):
+        tree = self.soup("<gar class='foo bar'>Found it</gar>")
+
+        f = tree.find_all("gar", class_=re.compile("o"))
+        self.assertSelects(f, ["Found it"])
+
+        f = tree.find_all("gar", class_=re.compile("a"))
+        self.assertSelects(f, ["Found it"])
+
+        # If the search fails to match the individual strings "foo" and "bar",
+        # it will be tried against the combined string "foo bar".
+        f = tree.find_all("gar", class_=re.compile("o b"))
+        self.assertSelects(f, ["Found it"])
+
+    def test_find_all_with_non_dictionary_for_attrs_finds_by_class(self):
+        soup = self.soup("<a class='bar'>Found it</a>")
+
+        self.assertSelects(soup.find_all("a", re.compile("ba")), ["Found it"])
+
+        def big_attribute_value(value):
+            return len(value) > 3
+
+        self.assertSelects(soup.find_all("a", big_attribute_value), [])
+
+        def small_attribute_value(value):
+            return len(value) <= 3
+
+        self.assertSelects(
+            soup.find_all("a", small_attribute_value), ["Found it"])
+
+    def test_find_all_with_string_for_attrs_finds_multiple_classes(self):
+        soup = self.soup('<a class="foo bar"></a><a class="foo"></a>')
+        a, a2 = soup.find_all("a")
+        self.assertEqual([a, a2], soup.find_all("a", "foo"))
+        self.assertEqual([a], soup.find_all("a", "bar"))
+
+        # If you specify the class as a string that contains a
+        # space, only that specific value will be found.
+        self.assertEqual([a], soup.find_all("a", class_="foo bar"))
+        self.assertEqual([a], soup.find_all("a", "foo bar"))
+        self.assertEqual([], soup.find_all("a", "bar foo"))
+
+    def test_find_all_by_attribute_soupstrainer(self):
+        tree = self.soup("""
+                         <a id="first">Match.</a>
+                         <a id="second">Non-match.</a>""")
+
+        strainer = SoupStrainer(attrs={'id' : 'first'})
+        self.assertSelects(tree.find_all(strainer), ['Match.'])
+
+    def test_find_all_with_missing_attribute(self):
+        # You can pass in None as the value of an attribute to find_all.
+        # This will match tags that do not have that attribute set.
+        tree = self.soup("""<a id="1">ID present.</a>
+                            <a>No ID present.</a>
+                            <a id="">ID is empty.</a>""")
+        self.assertSelects(tree.find_all('a', id=None), ["No ID present."])
+
+    def test_find_all_with_defined_attribute(self):
+        # You can pass in None as the value of an attribute to find_all.
+        # This will match tags that have that attribute set to any value.
+        tree = self.soup("""<a id="1">ID present.</a>
+                            <a>No ID present.</a>
+                            <a id="">ID is empty.</a>""")
+        self.assertSelects(
+            tree.find_all(id=True), ["ID present.", "ID is empty."])
+
+    def test_find_all_with_numeric_attribute(self):
+        # If you search for a number, it's treated as a string.
+        tree = self.soup("""<a id=1>Unquoted attribute.</a>
+                            <a id="1">Quoted attribute.</a>""")
+
+        expected = ["Unquoted attribute.", "Quoted attribute."]
+        self.assertSelects(tree.find_all(id=1), expected)
+        self.assertSelects(tree.find_all(id="1"), expected)
+
+    def test_find_all_with_list_attribute_values(self):
+        # You can pass a list of attribute values instead of just one,
+        # and you'll get tags that match any of the values.
+        tree = self.soup("""<a id="1">1</a>
+                            <a id="2">2</a>
+                            <a id="3">3</a>
+                            <a>No ID.</a>""")
+        self.assertSelects(tree.find_all(id=["1", "3", "4"]),
+                           ["1", "3"])
+
+    def test_find_all_with_regular_expression_attribute_value(self):
+        # You can pass a regular expression as an attribute value, and
+        # you'll get tags whose values for that attribute match the
+        # regular expression.
+        tree = self.soup("""<a id="a">One a.</a>
+                            <a id="aa">Two as.</a>
+                            <a id="ab">Mixed as and bs.</a>
+                            <a id="b">One b.</a>
+                            <a>No ID.</a>""")
+
+        self.assertSelects(tree.find_all(id=re.compile("^a+$")),
+                           ["One a.", "Two as."])
+
+    def test_find_by_name_and_containing_string(self):
+        soup = self.soup("<b>foo</b><b>bar</b><a>foo</a>")
+        a = soup.a
+
+        self.assertEqual([a], soup.find_all("a", text="foo"))
+        self.assertEqual([], soup.find_all("a", text="bar"))
+        self.assertEqual([], soup.find_all("a", text="bar"))
+
+    def test_find_by_name_and_containing_string_when_string_is_buried(self):
+        soup = self.soup("<a>foo</a><a><b><c>foo</c></b></a>")
+        self.assertEqual(soup.find_all("a"), soup.find_all("a", text="foo"))
+
+    def test_find_by_attribute_and_containing_string(self):
+        soup = self.soup('<b id="1">foo</b><a id="2">foo</a>')
+        a = soup.a
+
+        self.assertEqual([a], soup.find_all(id=2, text="foo"))
+        self.assertEqual([], soup.find_all(id=1, text="bar"))
+
+
+class TestSmooth(TreeTest):
+    """Test Tag.smooth."""
+
+    def test_smooth(self):
+        soup = self.soup("<div>a</div>")
+        div = soup.div
+        div.append("b")
+        div.append("c")
+        div.append(Comment("Comment 1"))
+        div.append(Comment("Comment 2"))
+        div.append("d")
+        builder = self.default_builder()
+        span = Tag(soup, builder, 'span')
+        span.append('1')
+        span.append('2')
+        div.append(span)
+
+        # At this point the tree has a bunch of adjacent
+        # NavigableStrings. This is normal, but it has no meaning in
+        # terms of HTML, so we may want to smooth things out for
+        # output.
+
+        # Since the <span> tag has two children, its .string is None.
+        self.assertEqual(None, div.span.string)
+
+        self.assertEqual(7, len(div.contents))
+        div.smooth()
+        self.assertEqual(5, len(div.contents))
+
+        # The three strings at the beginning of div.contents have been
+        # merged into on string.
+        #
+        self.assertEqual('abc', div.contents[0])
+
+        # The call is recursive -- the <span> tag was also smoothed.
+        self.assertEqual('12', div.span.string)
+
+        # The two comments have _not_ been merged, even though
+        # comments are strings. Merging comments would change the
+        # meaning of the HTML.
+        self.assertEqual('Comment 1', div.contents[1])
+        self.assertEqual('Comment 2', div.contents[2])
+
+
+class TestIndex(TreeTest):
+    """Test Tag.index"""
+    def test_index(self):
+        tree = self.soup("""<div>
+                            <a>Identical</a>
+                            <b>Not identical</b>
+                            <a>Identical</a>
+
+                            <c><d>Identical with child</d></c>
+                            <b>Also not identical</b>
+                            <c><d>Identical with child</d></c>
+                            </div>""")
+        div = tree.div
+        for i, element in enumerate(div.contents):
+            self.assertEqual(i, div.index(element))
+        self.assertRaises(ValueError, tree.index, 1)
+
+
+class TestParentOperations(TreeTest):
+    """Test navigation and searching through an element's parents."""
+
+    def setUp(self):
+        super(TestParentOperations, self).setUp()
+        self.tree = self.soup('''<ul id="empty"></ul>
+                                 <ul id="top">
+                                  <ul id="middle">
+                                   <ul id="bottom">
+                                    <b>Start here</b>
+                                   </ul>
+                                  </ul>''')
+        self.start = self.tree.b
+
+
+    def test_parent(self):
+        self.assertEqual(self.start.parent['id'], 'bottom')
+        self.assertEqual(self.start.parent.parent['id'], 'middle')
+        self.assertEqual(self.start.parent.parent.parent['id'], 'top')
+
+    def test_parent_of_top_tag_is_soup_object(self):
+        top_tag = self.tree.contents[0]
+        self.assertEqual(top_tag.parent, self.tree)
+
+    def test_soup_object_has_no_parent(self):
+        self.assertEqual(None, self.tree.parent)
+
+    def test_find_parents(self):
+        self.assertSelectsIDs(
+            self.start.find_parents('ul'), ['bottom', 'middle', 'top'])
+        self.assertSelectsIDs(
+            self.start.find_parents('ul', id="middle"), ['middle'])
+
+    def test_find_parent(self):
+        self.assertEqual(self.start.find_parent('ul')['id'], 'bottom')
+        self.assertEqual(self.start.find_parent('ul', id='top')['id'], 'top')
+
+    def test_parent_of_text_element(self):
+        text = self.tree.find(text="Start here")
+        self.assertEqual(text.parent.name, 'b')
+
+    def test_text_element_find_parent(self):
+        text = self.tree.find(text="Start here")
+        self.assertEqual(text.find_parent('ul')['id'], 'bottom')
+
+    def test_parent_generator(self):
+        parents = [parent['id'] for parent in self.start.parents
+                   if parent is not None and 'id' in parent.attrs]
+        self.assertEqual(parents, ['bottom', 'middle', 'top'])
+
+
+class ProximityTest(TreeTest):
+
+    def setUp(self):
+        super(TreeTest, self).setUp()
+        self.tree = self.soup(
+            '<html id="start"><head></head><body><b id="1">One</b><b id="2">Two</b><b id="3">Three</b></body></html>')
+
+
+class TestNextOperations(ProximityTest):
+
+    def setUp(self):
+        super(TestNextOperations, self).setUp()
+        self.start = self.tree.b
+
+    def test_next(self):
+        self.assertEqual(self.start.next_element, "One")
+        self.assertEqual(self.start.next_element.next_element['id'], "2")
+
+    def test_next_of_last_item_is_none(self):
+        last = self.tree.find(text="Three")
+        self.assertEqual(last.next_element, None)
+
+    def test_next_of_root_is_none(self):
+        # The document root is outside the next/previous chain.
+        self.assertEqual(self.tree.next_element, None)
+
+    def test_find_all_next(self):
+        self.assertSelects(self.start.find_all_next('b'), ["Two", "Three"])
+        self.start.find_all_next(id=3)
+        self.assertSelects(self.start.find_all_next(id=3), ["Three"])
+
+    def test_find_next(self):
+        self.assertEqual(self.start.find_next('b')['id'], '2')
+        self.assertEqual(self.start.find_next(text="Three"), "Three")
+
+    def test_find_next_for_text_element(self):
+        text = self.tree.find(text="One")
+        self.assertEqual(text.find_next("b").string, "Two")
+        self.assertSelects(text.find_all_next("b"), ["Two", "Three"])
+
+    def test_next_generator(self):
+        start = self.tree.find(text="Two")
+        successors = [node for node in start.next_elements]
+        # There are two successors: the final <b> tag and its text contents.
+        tag, contents = successors
+        self.assertEqual(tag['id'], '3')
+        self.assertEqual(contents, "Three")
+
+class TestPreviousOperations(ProximityTest):
+
+    def setUp(self):
+        super(TestPreviousOperations, self).setUp()
+        self.end = self.tree.find(text="Three")
+
+    def test_previous(self):
+        self.assertEqual(self.end.previous_element['id'], "3")
+        self.assertEqual(self.end.previous_element.previous_element, "Two")
+
+    def test_previous_of_first_item_is_none(self):
+        first = self.tree.find('html')
+        self.assertEqual(first.previous_element, None)
+
+    def test_previous_of_root_is_none(self):
+        # The document root is outside the next/previous chain.
+        # XXX This is broken!
+        #self.assertEqual(self.tree.previous_element, None)
+        pass
+
+    def test_find_all_previous(self):
+        # The <b> tag containing the "Three" node is the predecessor
+        # of the "Three" node itself, which is why "Three" shows up
+        # here.
+        self.assertSelects(
+            self.end.find_all_previous('b'), ["Three", "Two", "One"])
+        self.assertSelects(self.end.find_all_previous(id=1), ["One"])
+
+    def test_find_previous(self):
+        self.assertEqual(self.end.find_previous('b')['id'], '3')
+        self.assertEqual(self.end.find_previous(text="One"), "One")
+
+    def test_find_previous_for_text_element(self):
+        text = self.tree.find(text="Three")
+        self.assertEqual(text.find_previous("b").string, "Three")
+        self.assertSelects(
+            text.find_all_previous("b"), ["Three", "Two", "One"])
+
+    def test_previous_generator(self):
+        start = self.tree.find(text="One")
+        predecessors = [node for node in start.previous_elements]
+
+        # There are four predecessors: the <b> tag containing "One"
+        # the <body> tag, the <head> tag, and the <html> tag.
+        b, body, head, html = predecessors
+        self.assertEqual(b['id'], '1')
+        self.assertEqual(body.name, "body")
+        self.assertEqual(head.name, "head")
+        self.assertEqual(html.name, "html")
+
+
+class SiblingTest(TreeTest):
+
+    def setUp(self):
+        super(SiblingTest, self).setUp()
+        markup = '''<html>
+                    <span id="1">
+                     <span id="1.1"></span>
+                    </span>
+                    <span id="2">
+                     <span id="2.1"></span>
+                    </span>
+                    <span id="3">
+                     <span id="3.1"></span>
+                    </span>
+                    <span id="4"></span>
+                    </html>'''
+        # All that whitespace looks good but makes the tests more
+        # difficult. Get rid of it.
+        markup = re.compile(r"\n\s*").sub("", markup)
+        self.tree = self.soup(markup)
+
+
+class TestNextSibling(SiblingTest):
+
+    def setUp(self):
+        super(TestNextSibling, self).setUp()
+        self.start = self.tree.find(id="1")
+
+    def test_next_sibling_of_root_is_none(self):
+        self.assertEqual(self.tree.next_sibling, None)
+
+    def test_next_sibling(self):
+        self.assertEqual(self.start.next_sibling['id'], '2')
+        self.assertEqual(self.start.next_sibling.next_sibling['id'], '3')
+
+        # Note the difference between next_sibling and next_element.
+        self.assertEqual(self.start.next_element['id'], '1.1')
+
+    def test_next_sibling_may_not_exist(self):
+        self.assertEqual(self.tree.html.next_sibling, None)
+
+        nested_span = self.tree.find(id="1.1")
+        self.assertEqual(nested_span.next_sibling, None)
+
+        last_span = self.tree.find(id="4")
+        self.assertEqual(last_span.next_sibling, None)
+
+    def test_find_next_sibling(self):
+        self.assertEqual(self.start.find_next_sibling('span')['id'], '2')
+
+    def test_next_siblings(self):
+        self.assertSelectsIDs(self.start.find_next_siblings("span"),
+                              ['2', '3', '4'])
+
+        self.assertSelectsIDs(self.start.find_next_siblings(id='3'), ['3'])
+
+    def test_next_sibling_for_text_element(self):
+        soup = self.soup("Foo<b>bar</b>baz")
+        start = soup.find(text="Foo")
+        self.assertEqual(start.next_sibling.name, 'b')
+        self.assertEqual(start.next_sibling.next_sibling, 'baz')
+
+        self.assertSelects(start.find_next_siblings('b'), ['bar'])
+        self.assertEqual(start.find_next_sibling(text="baz"), "baz")
+        self.assertEqual(start.find_next_sibling(text="nonesuch"), None)
+
+
+class TestPreviousSibling(SiblingTest):
+
+    def setUp(self):
+        super(TestPreviousSibling, self).setUp()
+        self.end = self.tree.find(id="4")
+
+    def test_previous_sibling_of_root_is_none(self):
+        self.assertEqual(self.tree.previous_sibling, None)
+
+    def test_previous_sibling(self):
+        self.assertEqual(self.end.previous_sibling['id'], '3')
+        self.assertEqual(self.end.previous_sibling.previous_sibling['id'], '2')
+
+        # Note the difference between previous_sibling and previous_element.
+        self.assertEqual(self.end.previous_element['id'], '3.1')
+
+    def test_previous_sibling_may_not_exist(self):
+        self.assertEqual(self.tree.html.previous_sibling, None)
+
+        nested_span = self.tree.find(id="1.1")
+        self.assertEqual(nested_span.previous_sibling, None)
+
+        first_span = self.tree.find(id="1")
+        self.assertEqual(first_span.previous_sibling, None)
+
+    def test_find_previous_sibling(self):
+        self.assertEqual(self.end.find_previous_sibling('span')['id'], '3')
+
+    def test_previous_siblings(self):
+        self.assertSelectsIDs(self.end.find_previous_siblings("span"),
+                              ['3', '2', '1'])
+
+        self.assertSelectsIDs(self.end.find_previous_siblings(id='1'), ['1'])
+
+    def test_previous_sibling_for_text_element(self):
+        soup = self.soup("Foo<b>bar</b>baz")
+        start = soup.find(text="baz")
+        self.assertEqual(start.previous_sibling.name, 'b')
+        self.assertEqual(start.previous_sibling.previous_sibling, 'Foo')
+
+        self.assertSelects(start.find_previous_siblings('b'), ['bar'])
+        self.assertEqual(start.find_previous_sibling(text="Foo"), "Foo")
+        self.assertEqual(start.find_previous_sibling(text="nonesuch"), None)
+
+
+class TestTagCreation(SoupTest):
+    """Test the ability to create new tags."""
+    def test_new_tag(self):
+        soup = self.soup("")
+        new_tag = soup.new_tag("foo", bar="baz", attrs={"name": "a name"})
+        self.assertTrue(isinstance(new_tag, Tag))
+        self.assertEqual("foo", new_tag.name)
+        self.assertEqual(dict(bar="baz", name="a name"), new_tag.attrs)
+        self.assertEqual(None, new_tag.parent)
+        
+    def test_tag_inherits_self_closing_rules_from_builder(self):
+        if XML_BUILDER_PRESENT:
+            xml_soup = BeautifulSoup("", "lxml-xml")
+            xml_br = xml_soup.new_tag("br")
+            xml_p = xml_soup.new_tag("p")
+
+            # Both the <br> and <p> tag are empty-element, just because
+            # they have no contents.
+            self.assertEqual(b"<br/>", xml_br.encode())
+            self.assertEqual(b"<p/>", xml_p.encode())
+
+        html_soup = BeautifulSoup("", "html.parser")
+        html_br = html_soup.new_tag("br")
+        html_p = html_soup.new_tag("p")
+
+        # The HTML builder users HTML's rules about which tags are
+        # empty-element tags, and the new tags reflect these rules.
+        self.assertEqual(b"<br/>", html_br.encode())
+        self.assertEqual(b"<p></p>", html_p.encode())
+
+    def test_new_string_creates_navigablestring(self):
+        soup = self.soup("")
+        s = soup.new_string("foo")
+        self.assertEqual("foo", s)
+        self.assertTrue(isinstance(s, NavigableString))
+
+    def test_new_string_can_create_navigablestring_subclass(self):
+        soup = self.soup("")
+        s = soup.new_string("foo", Comment)
+        self.assertEqual("foo", s)
+        self.assertTrue(isinstance(s, Comment))
+
+class TestTreeModification(SoupTest):
+
+    def test_attribute_modification(self):
+        soup = self.soup('<a id="1"></a>')
+        soup.a['id'] = 2
+        self.assertEqual(soup.decode(), self.document_for('<a id="2"></a>'))
+        del(soup.a['id'])
+        self.assertEqual(soup.decode(), self.document_for('<a></a>'))
+        soup.a['id2'] = 'foo'
+        self.assertEqual(soup.decode(), self.document_for('<a id2="foo"></a>'))
+
+    def test_new_tag_creation(self):
+        builder = builder_registry.lookup('html')()
+        soup = self.soup("<body></body>", builder=builder)
+        a = Tag(soup, builder, 'a')
+        ol = Tag(soup, builder, 'ol')
+        a['href'] = 'http://foo.com/'
+        soup.body.insert(0, a)
+        soup.body.insert(1, ol)
+        self.assertEqual(
+            soup.body.encode(),
+            b'<body><a href="http://foo.com/"></a><ol></ol></body>')
+
+    def test_append_to_contents_moves_tag(self):
+        doc = """<p id="1">Don't leave me <b>here</b>.</p>
+                <p id="2">Don\'t leave!</p>"""
+        soup = self.soup(doc)
+        second_para = soup.find(id='2')
+        bold = soup.b
+
+        # Move the <b> tag to the end of the second paragraph.
+        soup.find(id='2').append(soup.b)
+
+        # The <b> tag is now a child of the second paragraph.
+        self.assertEqual(bold.parent, second_para)
+
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                '<p id="1">Don\'t leave me .</p>\n'
+                '<p id="2">Don\'t leave!<b>here</b></p>'))
+
+    def test_replace_with_returns_thing_that_was_replaced(self):
+        text = "<a></a><b><c></c></b>"
+        soup = self.soup(text)
+        a = soup.a
+        new_a = a.replace_with(soup.c)
+        self.assertEqual(a, new_a)
+
+    def test_unwrap_returns_thing_that_was_replaced(self):
+        text = "<a><b></b><c></c></a>"
+        soup = self.soup(text)
+        a = soup.a
+        new_a = a.unwrap()
+        self.assertEqual(a, new_a)
+
+    def test_replace_with_and_unwrap_give_useful_exception_when_tag_has_no_parent(self):
+        soup = self.soup("<a><b>Foo</b></a><c>Bar</c>")
+        a = soup.a
+        a.extract()
+        self.assertEqual(None, a.parent)
+        self.assertRaises(ValueError, a.unwrap)
+        self.assertRaises(ValueError, a.replace_with, soup.c)
+
+    def test_replace_tag_with_itself(self):
+        text = "<a><b></b><c>Foo<d></d></c></a><a><e></e></a>"
+        soup = self.soup(text)
+        c = soup.c
+        soup.c.replace_with(c)
+        self.assertEqual(soup.decode(), self.document_for(text))
+
+    def test_replace_tag_with_its_parent_raises_exception(self):
+        text = "<a><b></b></a>"
+        soup = self.soup(text)
+        self.assertRaises(ValueError, soup.b.replace_with, soup.a)
+
+    def test_insert_tag_into_itself_raises_exception(self):
+        text = "<a><b></b></a>"
+        soup = self.soup(text)
+        self.assertRaises(ValueError, soup.a.insert, 0, soup.a)
+
+    def test_insert_beautifulsoup_object_inserts_children(self):
+        """Inserting one BeautifulSoup object into another actually inserts all
+        of its children -- you'll never combine BeautifulSoup objects.
+        """
+        soup = self.soup("<p>And now, a word:</p><p>And we're back.</p>")
+        
+        text = "<p>p2</p><p>p3</p>"
+        to_insert = self.soup(text)
+        soup.insert(1, to_insert)
+
+        for i in soup.descendants:
+            assert not isinstance(i, BeautifulSoup)
+        
+        p1, p2, p3, p4 = list(soup.children)
+        self.assertEqual("And now, a word:", p1.string)
+        self.assertEqual("p2", p2.string)
+        self.assertEqual("p3", p3.string)
+        self.assertEqual("And we're back.", p4.string)
+        
+        
+    def test_replace_with_maintains_next_element_throughout(self):
+        soup = self.soup('<p><a>one</a><b>three</b></p>')
+        a = soup.a
+        b = a.contents[0]
+        # Make it so the <a> tag has two text children.
+        a.insert(1, "two")
+
+        # Now replace each one with the empty string.
+        left, right = a.contents
+        left.replaceWith('')
+        right.replaceWith('')
+
+        # The <b> tag is still connected to the tree.
+        self.assertEqual("three", soup.b.string)
+
+    def test_replace_final_node(self):
+        soup = self.soup("<b>Argh!</b>")
+        soup.find(text="Argh!").replace_with("Hooray!")
+        new_text = soup.find(text="Hooray!")
+        b = soup.b
+        self.assertEqual(new_text.previous_element, b)
+        self.assertEqual(new_text.parent, b)
+        self.assertEqual(new_text.previous_element.next_element, new_text)
+        self.assertEqual(new_text.next_element, None)
+
+    def test_consecutive_text_nodes(self):
+        # A builder should never create two consecutive text nodes,
+        # but if you insert one next to another, Beautiful Soup will
+        # handle it correctly.
+        soup = self.soup("<a><b>Argh!</b><c></c></a>")
+        soup.b.insert(1, "Hooray!")
+
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                "<a><b>Argh!Hooray!</b><c></c></a>"))
+
+        new_text = soup.find(text="Hooray!")
+        self.assertEqual(new_text.previous_element, "Argh!")
+        self.assertEqual(new_text.previous_element.next_element, new_text)
+
+        self.assertEqual(new_text.previous_sibling, "Argh!")
+        self.assertEqual(new_text.previous_sibling.next_sibling, new_text)
+
+        self.assertEqual(new_text.next_sibling, None)
+        self.assertEqual(new_text.next_element, soup.c)
+
+    def test_insert_string(self):
+        soup = self.soup("<a></a>")
+        soup.a.insert(0, "bar")
+        soup.a.insert(0, "foo")
+        # The string were added to the tag.
+        self.assertEqual(["foo", "bar"], soup.a.contents)
+        # And they were converted to NavigableStrings.
+        self.assertEqual(soup.a.contents[0].next_element, "bar")
+
+    def test_insert_tag(self):
+        builder = self.default_builder()
+        soup = self.soup(
+            "<a><b>Find</b><c>lady!</c><d></d></a>", builder=builder)
+        magic_tag = Tag(soup, builder, 'magictag')
+        magic_tag.insert(0, "the")
+        soup.a.insert(1, magic_tag)
+
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                "<a><b>Find</b><magictag>the</magictag><c>lady!</c><d></d></a>"))
+
+        # Make sure all the relationships are hooked up correctly.
+        b_tag = soup.b
+        self.assertEqual(b_tag.next_sibling, magic_tag)
+        self.assertEqual(magic_tag.previous_sibling, b_tag)
+
+        find = b_tag.find(text="Find")
+        self.assertEqual(find.next_element, magic_tag)
+        self.assertEqual(magic_tag.previous_element, find)
+
+        c_tag = soup.c
+        self.assertEqual(magic_tag.next_sibling, c_tag)
+        self.assertEqual(c_tag.previous_sibling, magic_tag)
+
+        the = magic_tag.find(text="the")
+        self.assertEqual(the.parent, magic_tag)
+        self.assertEqual(the.next_element, c_tag)
+        self.assertEqual(c_tag.previous_element, the)
+
+    def test_append_child_thats_already_at_the_end(self):
+        data = "<a><b></b></a>"
+        soup = self.soup(data)
+        soup.a.append(soup.b)
+        self.assertEqual(data, soup.decode())
+
+    def test_extend(self):
+        data = "<a><b><c><d><e><f><g></g></f></e></d></c></b></a>"
+        soup = self.soup(data)
+        l = [soup.g, soup.f, soup.e, soup.d, soup.c, soup.b]
+        soup.a.extend(l)
+        self.assertEqual("<a><g></g><f></f><e></e><d></d><c></c><b></b></a>", soup.decode())
+
+    def test_move_tag_to_beginning_of_parent(self):
+        data = "<a><b></b><c></c><d></d></a>"
+        soup = self.soup(data)
+        soup.a.insert(0, soup.d)
+        self.assertEqual("<a><d></d><b></b><c></c></a>", soup.decode())
+
+    def test_insert_works_on_empty_element_tag(self):
+        # This is a little strange, since most HTML parsers don't allow
+        # markup like this to come through. But in general, we don't
+        # know what the parser would or wouldn't have allowed, so
+        # I'm letting this succeed for now.
+        soup = self.soup("<br/>")
+        soup.br.insert(1, "Contents")
+        self.assertEqual(str(soup.br), "<br>Contents</br>")
+
+    def test_insert_before(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_before("BAZ")
+        soup.a.insert_before("QUUX")
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX<a>foo</a>BAZ<b>bar</b>"))
+
+        soup.a.insert_before(soup.b)
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX<b>bar</b><a>foo</a>BAZ"))
+
+        # Can't insert an element before itself.
+        b = soup.b
+        self.assertRaises(ValueError, b.insert_before, b)
+
+        # Can't insert before if an element has no parent.
+        b.extract()
+        self.assertRaises(ValueError, b.insert_before, "nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
+        
+    def test_insert_multiple_before(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_before("BAZ", " ", "QUUX")
+        soup.a.insert_before("QUUX", " ", "BAZ")
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX BAZ<a>foo</a>BAZ QUUX<b>bar</b>"))
+
+        soup.a.insert_before(soup.b, "FOO")
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX BAZ<b>bar</b>FOO<a>foo</a>BAZ QUUX"))
+
+    def test_insert_after(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_after("BAZ")
+        soup.a.insert_after("QUUX")
+        self.assertEqual(
+            soup.decode(), self.document_for("<a>foo</a>QUUX<b>bar</b>BAZ"))
+        soup.b.insert_after(soup.a)
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX<b>bar</b><a>foo</a>BAZ"))
+
+        # Can't insert an element after itself.
+        b = soup.b
+        self.assertRaises(ValueError, b.insert_after, b)
+
+        # Can't insert after if an element has no parent.
+        b.extract()
+        self.assertRaises(ValueError, b.insert_after, "nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
+        
+    def test_insert_multiple_after(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_after("BAZ", " ", "QUUX")
+        soup.a.insert_after("QUUX", " ", "BAZ")
+        self.assertEqual(
+            soup.decode(), self.document_for("<a>foo</a>QUUX BAZ<b>bar</b>BAZ QUUX"))
+        soup.b.insert_after(soup.a, "FOO ")
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX BAZ<b>bar</b><a>foo</a>FOO BAZ QUUX"))
+
+    def test_insert_after_raises_exception_if_after_has_no_meaning(self):
+        soup = self.soup("")
+        tag = soup.new_tag("a")
+        string = soup.new_string("")
+        self.assertRaises(ValueError, string.insert_after, tag)
+        self.assertRaises(NotImplementedError, soup.insert_after, tag)
+        self.assertRaises(ValueError, tag.insert_after, tag)
+
+    def test_insert_before_raises_notimplementederror_if_before_has_no_meaning(self):
+        soup = self.soup("")
+        tag = soup.new_tag("a")
+        string = soup.new_string("")
+        self.assertRaises(ValueError, string.insert_before, tag)
+        self.assertRaises(NotImplementedError, soup.insert_before, tag)
+        self.assertRaises(ValueError, tag.insert_before, tag)
+
+    def test_replace_with(self):
+        soup = self.soup(
+                "<p>There's <b>no</b> business like <b>show</b> business</p>")
+        no, show = soup.find_all('b')
+        show.replace_with(no)
+        self.assertEqual(
+            soup.decode(),
+            self.document_for(
+                "<p>There's  business like <b>no</b> business</p>"))
+
+        self.assertEqual(show.parent, None)
+        self.assertEqual(no.parent, soup.p)
+        self.assertEqual(no.next_element, "no")
+        self.assertEqual(no.next_sibling, " business")
+
+    def test_replace_first_child(self):
+        data = "<a><b></b><c></c></a>"
+        soup = self.soup(data)
+        soup.b.replace_with(soup.c)
+        self.assertEqual("<a><c></c></a>", soup.decode())
+
+    def test_replace_last_child(self):
+        data = "<a><b></b><c></c></a>"
+        soup = self.soup(data)
+        soup.c.replace_with(soup.b)
+        self.assertEqual("<a><b></b></a>", soup.decode())
+
+    def test_nested_tag_replace_with(self):
+        soup = self.soup(
+            """<a>We<b>reserve<c>the</c><d>right</d></b></a><e>to<f>refuse</f><g>service</g></e>""")
+
+        # Replace the entire <b> tag and its contents ("reserve the
+        # right") with the <f> tag ("refuse").
+        remove_tag = soup.b
+        move_tag = soup.f
+        remove_tag.replace_with(move_tag)
+
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                "<a>We<f>refuse</f></a><e>to<g>service</g></e>"))
+
+        # The <b> tag is now an orphan.
+        self.assertEqual(remove_tag.parent, None)
+        self.assertEqual(remove_tag.find(text="right").next_element, None)
+        self.assertEqual(remove_tag.previous_element, None)
+        self.assertEqual(remove_tag.next_sibling, None)
+        self.assertEqual(remove_tag.previous_sibling, None)
+
+        # The <f> tag is now connected to the <a> tag.
+        self.assertEqual(move_tag.parent, soup.a)
+        self.assertEqual(move_tag.previous_element, "We")
+        self.assertEqual(move_tag.next_element.next_element, soup.e)
+        self.assertEqual(move_tag.next_sibling, None)
+
+        # The gap where the <f> tag used to be has been mended, and
+        # the word "to" is now connected to the <g> tag.
+        to_text = soup.find(text="to")
+        g_tag = soup.g
+        self.assertEqual(to_text.next_element, g_tag)
+        self.assertEqual(to_text.next_sibling, g_tag)
+        self.assertEqual(g_tag.previous_element, to_text)
+        self.assertEqual(g_tag.previous_sibling, to_text)
+
+    def test_unwrap(self):
+        tree = self.soup("""
+            <p>Unneeded <em>formatting</em> is unneeded</p>
+            """)
+        tree.em.unwrap()
+        self.assertEqual(tree.em, None)
+        self.assertEqual(tree.p.text, "Unneeded formatting is unneeded")
+
+    def test_wrap(self):
+        soup = self.soup("I wish I was bold.")
+        value = soup.string.wrap(soup.new_tag("b"))
+        self.assertEqual(value.decode(), "<b>I wish I was bold.</b>")
+        self.assertEqual(
+            soup.decode(), self.document_for("<b>I wish I was bold.</b>"))
+
+    def test_wrap_extracts_tag_from_elsewhere(self):
+        soup = self.soup("<b></b>I wish I was bold.")
+        soup.b.next_sibling.wrap(soup.b)
+        self.assertEqual(
+            soup.decode(), self.document_for("<b>I wish I was bold.</b>"))
+
+    def test_wrap_puts_new_contents_at_the_end(self):
+        soup = self.soup("<b>I like being bold.</b>I wish I was bold.")
+        soup.b.next_sibling.wrap(soup.b)
+        self.assertEqual(2, len(soup.b.contents))
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                "<b>I like being bold.I wish I was bold.</b>"))
+
+    def test_extract(self):
+        soup = self.soup(
+            '<html><body>Some content. <div id="nav">Nav crap</div> More content.</body></html>')
+
+        self.assertEqual(len(soup.body.contents), 3)
+        extracted = soup.find(id="nav").extract()
+
+        self.assertEqual(
+            soup.decode(), "<html><body>Some content.  More content.</body></html>")
+        self.assertEqual(extracted.decode(), '<div id="nav">Nav crap</div>')
+
+        # The extracted tag is now an orphan.
+        self.assertEqual(len(soup.body.contents), 2)
+        self.assertEqual(extracted.parent, None)
+        self.assertEqual(extracted.previous_element, None)
+        self.assertEqual(extracted.next_element.next_element, None)
+
+        # The gap where the extracted tag used to be has been mended.
+        content_1 = soup.find(text="Some content. ")
+        content_2 = soup.find(text=" More content.")
+        self.assertEqual(content_1.next_element, content_2)
+        self.assertEqual(content_1.next_sibling, content_2)
+        self.assertEqual(content_2.previous_element, content_1)
+        self.assertEqual(content_2.previous_sibling, content_1)
+
+    def test_extract_distinguishes_between_identical_strings(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        foo_1 = soup.a.string
+        bar_1 = soup.b.string
+        foo_2 = soup.new_string("foo")
+        bar_2 = soup.new_string("bar")
+        soup.a.append(foo_2)
+        soup.b.append(bar_2)
+
+        # Now there are two identical strings in the <a> tag, and two
+        # in the <b> tag. Let's remove the first "foo" and the second
+        # "bar".
+        foo_1.extract()
+        bar_2.extract()
+        self.assertEqual(foo_2, soup.a.string)
+        self.assertEqual(bar_2, soup.b.string)
+
+    def test_extract_multiples_of_same_tag(self):
+        soup = self.soup("""
+<html>
+<head>
+<script>foo</script>
+</head>
+<body>
+ <script>bar</script>
+ <a></a>
+</body>
+<script>baz</script>
+</html>""")
+        [soup.script.extract() for i in soup.find_all("script")]
+        self.assertEqual("<body>\n\n<a></a>\n</body>", str(soup.body))
+
+
+    def test_extract_works_when_element_is_surrounded_by_identical_strings(self):
+        soup = self.soup(
+ '<html>\n'
+ '<body>hi</body>\n'
+ '</html>')
+        soup.find('body').extract()
+        self.assertEqual(None, soup.find('body'))
+
+
+    def test_clear(self):
+        """Tag.clear()"""
+        soup = self.soup("<p><a>String <em>Italicized</em></a> and another</p>")
+        # clear using extract()
+        a = soup.a
+        soup.p.clear()
+        self.assertEqual(len(soup.p.contents), 0)
+        self.assertTrue(hasattr(a, "contents"))
+
+        # clear using decompose()
+        em = a.em
+        a.clear(decompose=True)
+        self.assertEqual(0, len(em.contents))
+
+    def test_string_set(self):
+        """Tag.string = 'string'"""
+        soup = self.soup("<a></a> <b><c></c></b>")
+        soup.a.string = "foo"
+        self.assertEqual(soup.a.contents, ["foo"])
+        soup.b.string = "bar"
+        self.assertEqual(soup.b.contents, ["bar"])
+
+    def test_string_set_does_not_affect_original_string(self):
+        soup = self.soup("<a><b>foo</b><c>bar</c>")
+        soup.b.string = soup.c.string
+        self.assertEqual(soup.a.encode(), b"<a><b>bar</b><c>bar</c></a>")
+
+    def test_set_string_preserves_class_of_string(self):
+        soup = self.soup("<a></a>")
+        cdata = CData("foo")
+        soup.a.string = cdata
+        self.assertTrue(isinstance(soup.a.string, CData))
+
+class TestElementObjects(SoupTest):
+    """Test various features of element objects."""
+
+    def test_len(self):
+        """The length of an element is its number of children."""
+        soup = self.soup("<top>1<b>2</b>3</top>")
+
+        # The BeautifulSoup object itself contains one element: the
+        # <top> tag.
+        self.assertEqual(len(soup.contents), 1)
+        self.assertEqual(len(soup), 1)
+
+        # The <top> tag contains three elements: the text node "1", the
+        # <b> tag, and the text node "3".
+        self.assertEqual(len(soup.top), 3)
+        self.assertEqual(len(soup.top.contents), 3)
+
+    def test_member_access_invokes_find(self):
+        """Accessing a Python member .foo invokes find('foo')"""
+        soup = self.soup('<b><i></i></b>')
+        self.assertEqual(soup.b, soup.find('b'))
+        self.assertEqual(soup.b.i, soup.find('b').find('i'))
+        self.assertEqual(soup.a, None)
+
+    def test_deprecated_member_access(self):
+        soup = self.soup('<b><i></i></b>')
+        with warnings.catch_warnings(record=True) as w:
+            tag = soup.bTag
+        self.assertEqual(soup.b, tag)
+        self.assertEqual(
+            '.bTag is deprecated, use .find("b") instead. If you really were looking for a tag called bTag, use .find("bTag")',
+            str(w[0].message))
+
+    def test_has_attr(self):
+        """has_attr() checks for the presence of an attribute.
+
+        Please note note: has_attr() is different from
+        __in__. has_attr() checks the tag's attributes and __in__
+        checks the tag's chidlren.
+        """
+        soup = self.soup("<foo attr='bar'>")
+        self.assertTrue(soup.foo.has_attr('attr'))
+        self.assertFalse(soup.foo.has_attr('attr2'))
+
+
+    def test_attributes_come_out_in_alphabetical_order(self):
+        markup = '<b a="1" z="5" m="3" f="2" y="4"></b>'
+        self.assertSoupEquals(markup, '<b a="1" f="2" m="3" y="4" z="5"></b>')
+
+    def test_string(self):
+        # A tag that contains only a text node makes that node
+        # available as .string.
+        soup = self.soup("<b>foo</b>")
+        self.assertEqual(soup.b.string, 'foo')
+
+    def test_empty_tag_has_no_string(self):
+        # A tag with no children has no .stirng.
+        soup = self.soup("<b></b>")
+        self.assertEqual(soup.b.string, None)
+
+    def test_tag_with_multiple_children_has_no_string(self):
+        # A tag with no children has no .string.
+        soup = self.soup("<a>foo<b></b><b></b></b>")
+        self.assertEqual(soup.b.string, None)
+
+        soup = self.soup("<a>foo<b></b>bar</b>")
+        self.assertEqual(soup.b.string, None)
+
+        # Even if all the children are strings, due to trickery,
+        # it won't work--but this would be a good optimization.
+        soup = self.soup("<a>foo</b>")
+        soup.a.insert(1, "bar")
+        self.assertEqual(soup.a.string, None)
+
+    def test_tag_with_recursive_string_has_string(self):
+        # A tag with a single child which has a .string inherits that
+        # .string.
+        soup = self.soup("<a><b>foo</b></a>")
+        self.assertEqual(soup.a.string, "foo")
+        self.assertEqual(soup.string, "foo")
+
+    def test_lack_of_string(self):
+        """Only a tag containing a single text node has a .string."""
+        soup = self.soup("<b>f<i>e</i>o</b>")
+        self.assertFalse(soup.b.string)
+
+        soup = self.soup("<b></b>")
+        self.assertFalse(soup.b.string)
+
+    def test_all_text(self):
+        """Tag.text and Tag.get_text(sep=u"") -> all child text, concatenated"""
+        soup = self.soup("<a>a<b>r</b>   <r> t </r></a>")
+        self.assertEqual(soup.a.text, "ar  t ")
+        self.assertEqual(soup.a.get_text(strip=True), "art")
+        self.assertEqual(soup.a.get_text(","), "a,r, , t ")
+        self.assertEqual(soup.a.get_text(",", strip=True), "a,r,t")
+
+    def test_get_text_ignores_comments(self):
+        soup = self.soup("foo<!--IGNORE-->bar")
+        self.assertEqual(soup.get_text(), "foobar")
+
+        self.assertEqual(
+            soup.get_text(types=(NavigableString, Comment)), "fooIGNOREbar")
+        self.assertEqual(
+            soup.get_text(types=None), "fooIGNOREbar")
+
+    def test_all_strings_ignores_comments(self):
+        soup = self.soup("foo<!--IGNORE-->bar")
+        self.assertEqual(['foo', 'bar'], list(soup.strings))
+
+class TestCDAtaListAttributes(SoupTest):
+
+    """Testing cdata-list attributes like 'class'.
+    """
+    def test_single_value_becomes_list(self):
+        soup = self.soup("<a class='foo'>")
+        self.assertEqual(["foo"],soup.a['class'])
+
+    def test_multiple_values_becomes_list(self):
+        soup = self.soup("<a class='foo bar'>")
+        self.assertEqual(["foo", "bar"], soup.a['class'])
+
+    def test_multiple_values_separated_by_weird_whitespace(self):
+        soup = self.soup("<a class='foo\tbar\nbaz'>")
+        self.assertEqual(["foo", "bar", "baz"],soup.a['class'])
+
+    def test_attributes_joined_into_string_on_output(self):
+        soup = self.soup("<a class='foo\tbar'>")
+        self.assertEqual(b'<a class="foo bar"></a>', soup.a.encode())
+
+    def test_get_attribute_list(self):
+        soup = self.soup("<a id='abc def'>")
+        self.assertEqual(['abc def'], soup.a.get_attribute_list('id'))
+        
+    def test_accept_charset(self):
+        soup = self.soup('<form accept-charset="ISO-8859-1 UTF-8">')
+        self.assertEqual(['ISO-8859-1', 'UTF-8'], soup.form['accept-charset'])
+
+    def test_cdata_attribute_applying_only_to_one_tag(self):
+        data = '<a accept-charset="ISO-8859-1 UTF-8"></a>'
+        soup = self.soup(data)
+        # We saw in another test that accept-charset is a cdata-list
+        # attribute for the <form> tag. But it's not a cdata-list
+        # attribute for any other tag.
+        self.assertEqual('ISO-8859-1 UTF-8', soup.a['accept-charset'])
+
+    def test_string_has_immutable_name_property(self):
+        string = self.soup("s").string
+        self.assertEqual(None, string.name)
+        def t():
+            string.name = 'foo'
+        self.assertRaises(AttributeError, t)
+
+class TestPersistence(SoupTest):
+    "Testing features like pickle and deepcopy."
+
+    def setUp(self):
+        super(TestPersistence, self).setUp()
+        self.page = """<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
+"http://www.w3.org/TR/REC-html40/transitional.dtd">
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<title>Beautiful Soup: We called him Tortoise because he taught us.</title>
+<link rev="made" href="mailto:[email protected]">
+<meta name="Description" content="Beautiful Soup: an HTML parser optimized for screen-scraping.">
+<meta name="generator" content="Markov Approximation 1.4 (module: leonardr)">
+<meta name="author" content="Leonard Richardson">
+</head>
+<body>
+<a href="foo">foo</a>
+<a href="foo"><b>bar</b></a>
+</body>
+</html>"""
+        self.tree = self.soup(self.page)
+
+    def test_pickle_and_unpickle_identity(self):
+        # Pickling a tree, then unpickling it, yields a tree identical
+        # to the original.
+        dumped = pickle.dumps(self.tree, 2)
+        loaded = pickle.loads(dumped)
+        self.assertEqual(loaded.__class__, BeautifulSoup)
+        self.assertEqual(loaded.decode(), self.tree.decode())
+
+    def test_deepcopy_identity(self):
+        # Making a deepcopy of a tree yields an identical tree.
+        copied = copy.deepcopy(self.tree)
+        self.assertEqual(copied.decode(), self.tree.decode())
+
+    def test_copy_preserves_encoding(self):
+        soup = BeautifulSoup(b'<p>&nbsp;</p>', 'html.parser')
+        encoding = soup.original_encoding
+        copy = soup.__copy__()
+        self.assertEqual("<p> </p>", str(copy))
+        self.assertEqual(encoding, copy.original_encoding)
+
+    def test_unicode_pickle(self):
+        # A tree containing Unicode characters can be pickled.
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        dumped = pickle.dumps(soup, pickle.HIGHEST_PROTOCOL)
+        loaded = pickle.loads(dumped)
+        self.assertEqual(loaded.decode(), soup.decode())
+
+    def test_copy_navigablestring_is_not_attached_to_tree(self):
+        html = "<b>Foo<a></a></b><b>Bar</b>"
+        soup = self.soup(html)
+        s1 = soup.find(string="Foo")
+        s2 = copy.copy(s1)
+        self.assertEqual(s1, s2)
+        self.assertEqual(None, s2.parent)
+        self.assertEqual(None, s2.next_element)
+        self.assertNotEqual(None, s1.next_sibling)
+        self.assertEqual(None, s2.next_sibling)
+        self.assertEqual(None, s2.previous_element)
+
+    def test_copy_navigablestring_subclass_has_same_type(self):
+        html = "<b><!--Foo--></b>"
+        soup = self.soup(html)
+        s1 = soup.string
+        s2 = copy.copy(s1)
+        self.assertEqual(s1, s2)
+        self.assertTrue(isinstance(s2, Comment))
+
+    def test_copy_entire_soup(self):
+        html = "<div><b>Foo<a></a></b><b>Bar</b></div>end"
+        soup = self.soup(html)
+        soup_copy = copy.copy(soup)
+        self.assertEqual(soup, soup_copy)
+
+    def test_copy_tag_copies_contents(self):
+        html = "<div><b>Foo<a></a></b><b>Bar</b></div>end"
+        soup = self.soup(html)
+        div = soup.div
+        div_copy = copy.copy(div)
+
+        # The two tags look the same, and evaluate to equal.
+        self.assertEqual(str(div), str(div_copy))
+        self.assertEqual(div, div_copy)
+
+        # But they're not the same object.
+        self.assertFalse(div is div_copy)
+
+        # And they don't have the same relation to the parse tree. The
+        # copy is not associated with a parse tree at all.
+        self.assertEqual(None, div_copy.parent)
+        self.assertEqual(None, div_copy.previous_element)
+        self.assertEqual(None, div_copy.find(string='Bar').next_element)
+        self.assertNotEqual(None, div.find(string='Bar').next_element)
+
+class TestSubstitutions(SoupTest):
+
+    def test_default_formatter_is_minimal(self):
+        markup = "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="minimal")
+        # The < is converted back into &lt; but the e-with-acute is left alone.
+        self.assertEqual(
+            decoded,
+            self.document_for(
+                "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"))
+
+    def test_formatter_html(self):
+        markup = "<br><b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="html")
+        self.assertEqual(
+            decoded,
+            self.document_for("<br/><b>&lt;&lt;Sacr&eacute; bleu!&gt;&gt;</b>"))
+
+    def test_formatter_html5(self):
+        markup = "<br><b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="html5")
+        self.assertEqual(
+            decoded,
+            self.document_for("<br><b>&lt;&lt;Sacr&eacute; bleu!&gt;&gt;</b>"))
+        
+    def test_formatter_minimal(self):
+        markup = "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="minimal")
+        # The < is converted back into &lt; but the e-with-acute is left alone.
+        self.assertEqual(
+            decoded,
+            self.document_for(
+                "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"))
+
+    def test_formatter_null(self):
+        markup = "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter=None)
+        # Neither the angle brackets nor the e-with-acute are converted.
+        # This is not valid HTML, but it's what the user wanted.
+        self.assertEqual(decoded,
+                          self.document_for("<b><<Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!>></b>"))
+
+    def test_formatter_custom(self):
+        markup = "<b>&lt;foo&gt;</b><b>bar</b><br/>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter = lambda x: x.upper())
+        # Instead of normal entity conversion code, the custom
+        # callable is called on every string.
+        self.assertEqual(
+            decoded,
+            self.document_for("<b><FOO></b><b>BAR</b><br/>"))
+
+    def test_formatter_is_run_on_attribute_values(self):
+        markup = '<a href="http://a.com?a=b&c=é">e</a>'
+        soup = self.soup(markup)
+        a = soup.a
+
+        expect_minimal = '<a href="http://a.com?a=b&amp;c=é">e</a>'
+
+        self.assertEqual(expect_minimal, a.decode())
+        self.assertEqual(expect_minimal, a.decode(formatter="minimal"))
+
+        expect_html = '<a href="http://a.com?a=b&amp;c=&eacute;">e</a>'
+        self.assertEqual(expect_html, a.decode(formatter="html"))
+
+        self.assertEqual(markup, a.decode(formatter=None))
+        expect_upper = '<a href="HTTP://A.COM?A=B&C=É">E</a>'
+        self.assertEqual(expect_upper, a.decode(formatter=lambda x: x.upper()))
+
+    def test_formatter_skips_script_tag_for_html_documents(self):
+        doc = """
+  <script type="text/javascript">
+   console.log("< < hey > > ");
+  </script>
+"""
+        encoded = BeautifulSoup(doc, 'html.parser').encode()
+        self.assertTrue(b"< < hey > >" in encoded)
+
+    def test_formatter_skips_style_tag_for_html_documents(self):
+        doc = """
+  <style type="text/css">
+   console.log("< < hey > > ");
+  </style>
+"""
+        encoded = BeautifulSoup(doc, 'html.parser').encode()
+        self.assertTrue(b"< < hey > >" in encoded)
+
+    def test_prettify_leaves_preformatted_text_alone(self):
+        soup = self.soup("<div>  foo  <pre>  \tbar\n  \n  </pre>  baz  <textarea> eee\nfff\t</textarea></div>")
+        # Everything outside the <pre> tag is reformatted, but everything
+        # inside is left alone.
+        self.assertEqual(
+            '<div>\n foo\n <pre>  \tbar\n  \n  </pre>\n baz\n <textarea> eee\nfff\t</textarea>\n</div>',
+            soup.div.prettify())
+
+    def test_prettify_accepts_formatter_function(self):
+        soup = BeautifulSoup("<html><body>foo</body></html>", 'html.parser')
+        pretty = soup.prettify(formatter = lambda x: x.upper())
+        self.assertTrue("FOO" in pretty)
+
+    def test_prettify_outputs_unicode_by_default(self):
+        soup = self.soup("<a></a>")
+        self.assertEqual(str, type(soup.prettify()))
+
+    def test_prettify_can_encode_data(self):
+        soup = self.soup("<a></a>")
+        self.assertEqual(bytes, type(soup.prettify("utf-8")))
+
+    def test_html_entity_substitution_off_by_default(self):
+        markup = "<b>Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!</b>"
+        soup = self.soup(markup)
+        encoded = soup.b.encode("utf-8")
+        self.assertEqual(encoded, markup.encode('utf-8'))
+
+    def test_encoding_substitution(self):
+        # Here's the <meta> tag saying that a document is
+        # encoded in Shift-JIS.
+        meta_tag = ('<meta content="text/html; charset=x-sjis" '
+                    'http-equiv="Content-type"/>')
+        soup = self.soup(meta_tag)
+
+        # Parse the document, and the charset apprears unchanged.
+        self.assertEqual(soup.meta['content'], 'text/html; charset=x-sjis')
+
+        # Encode the document into some encoding, and the encoding is
+        # substituted into the meta tag.
+        utf_8 = soup.encode("utf-8")
+        self.assertTrue(b"charset=utf-8" in utf_8)
+
+        euc_jp = soup.encode("euc_jp")
+        self.assertTrue(b"charset=euc_jp" in euc_jp)
+
+        shift_jis = soup.encode("shift-jis")
+        self.assertTrue(b"charset=shift-jis" in shift_jis)
+
+        utf_16_u = soup.encode("utf-16").decode("utf-16")
+        self.assertTrue("charset=utf-16" in utf_16_u)
+
+    def test_encoding_substitution_doesnt_happen_if_tag_is_strained(self):
+        markup = ('<head><meta content="text/html; charset=x-sjis" '
+                    'http-equiv="Content-type"/></head><pre>foo</pre>')
+
+        # Beautiful Soup used to try to rewrite the meta tag even if the
+        # meta tag got filtered out by the strainer. This test makes
+        # sure that doesn't happen.
+        strainer = SoupStrainer('pre')
+        soup = self.soup(markup, parse_only=strainer)
+        self.assertEqual(soup.contents[0].name, 'pre')
+
+class TestEncoding(SoupTest):
+    """Test the ability to encode objects into strings."""
+
+    def test_unicode_string_can_be_encoded(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(soup.b.string.encode("utf-8"),
+                          "\N{SNOWMAN}".encode("utf-8"))
+
+    def test_tag_containing_unicode_string_can_be_encoded(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(
+            soup.b.encode("utf-8"), html.encode("utf-8"))
+
+    def test_encoding_substitutes_unrecognized_characters_by_default(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(soup.b.encode("ascii"), b"<b>&#9731;</b>")
+
+    def test_encoding_can_be_made_strict(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertRaises(
+            UnicodeEncodeError, soup.encode, "ascii", errors="strict")
+
+    def test_decode_contents(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual("\N{SNOWMAN}", soup.b.decode_contents())
+
+    def test_encode_contents(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(
+            "\N{SNOWMAN}".encode("utf8"), soup.b.encode_contents(
+                encoding="utf8"))
+
+    def test_deprecated_renderContents(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(
+            "\N{SNOWMAN}".encode("utf8"), soup.b.renderContents())
+
+    def test_repr(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        if PY3K:
+            self.assertEqual(html, repr(soup))
+        else:
+            self.assertEqual(b'<b>\\u2603</b>', repr(soup))
+
+class TestFormatter(SoupTest):
+
+    def test_sort_attributes(self):
+        # Test the ability to override Formatter.attributes() to,
+        # e.g., disable the normal sorting of attributes.
+        class UnsortedFormatter(Formatter):
+            def attributes(self, tag):
+                self.called_with = tag
+                for k, v in sorted(tag.attrs.items()):
+                    if k == 'ignore':
+                        continue
+                    yield k,v
+
+        soup = self.soup('<p cval="1" aval="2" ignore="ignored"></p>')
+        formatter = UnsortedFormatter()
+        decoded = soup.decode(formatter=formatter)
+
+        # attributes() was called on the <p> tag. It filtered out one
+        # attribute and sorted the other two.
+        self.assertEqual(formatter.called_with, soup.p)
+        self.assertEqual('<p aval="2" cval="1"></p>', decoded)
+
+
+class TestNavigableStringSubclasses(SoupTest):
+
+    def test_cdata(self):
+        # None of the current builders turn CDATA sections into CData
+        # objects, but you can create them manually.
+        soup = self.soup("")
+        cdata = CData("foo")
+        soup.insert(1, cdata)
+        self.assertEqual(str(soup), "<![CDATA[foo]]>")
+        self.assertEqual(soup.find(text="foo"), "foo")
+        self.assertEqual(soup.contents[0], "foo")
+
+    def test_cdata_is_never_formatted(self):
+        """Text inside a CData object is passed into the formatter.
+
+        But the return value is ignored.
+        """
+
+        self.count = 0
+        def increment(*args):
+            self.count += 1
+            return "BITTER FAILURE"
+
+        soup = self.soup("")
+        cdata = CData("<><><>")
+        soup.insert(1, cdata)
+        self.assertEqual(
+            b"<![CDATA[<><><>]]>", soup.encode(formatter=increment))
+        self.assertEqual(1, self.count)
+
+    def test_doctype_ends_in_newline(self):
+        # Unlike other NavigableString subclasses, a DOCTYPE always ends
+        # in a newline.
+        doctype = Doctype("foo")
+        soup = self.soup("")
+        soup.insert(1, doctype)
+        self.assertEqual(soup.encode(), b"<!DOCTYPE foo>\n")
+
+    def test_declaration(self):
+        d = Declaration("foo")
+        self.assertEqual("<?foo?>", d.output_ready())
+
+class TestSoupSelector(TreeTest):
+
+    HTML = """
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+"http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<title>The title</title>
+<link rel="stylesheet" href="blah.css" type="text/css" id="l1">
+</head>
+<body>
+<custom-dashed-tag class="dashed" id="dash1">Hello there.</custom-dashed-tag>
+<div id="main" class="fancy">
+<div id="inner">
+<h1 id="header1">An H1</h1>
+<p>Some text</p>
+<p class="onep" id="p1">Some more text</p>
+<h2 id="header2">An H2</h2>
+<p class="class1 class2 class3" id="pmulti">Another</p>
+<a href="http://bob.example.org/" rel="friend met" id="bob">Bob</a>
+<h2 id="header3">Another H2</h2>
+<a id="me" href="http://simonwillison.net/" rel="me">me</a>
+<span class="s1">
+<a href="#" id="s1a1">span1a1</a>
+<a href="#" id="s1a2">span1a2 <span id="s1a2s1">test</span></a>
+<span class="span2">
+<a href="#" id="s2a1">span2a1</a>
+</span>
+<span class="span3"></span>
+<custom-dashed-tag class="dashed" id="dash2"/>
+<div data-tag="dashedvalue" id="data1"/>
+</span>
+</div>
+<x id="xid">
+<z id="zida"/>
+<z id="zidab"/>
+<z id="zidac"/>
+</x>
+<y id="yid">
+<z id="zidb"/>
+</y>
+<p lang="en" id="lang-en">English</p>
+<p lang="en-gb" id="lang-en-gb">English UK</p>
+<p lang="en-us" id="lang-en-us">English US</p>
+<p lang="fr" id="lang-fr">French</p>
+</div>
+
+<div id="footer">
+</div>
+"""
+
+    def setUp(self):
+        self.soup = BeautifulSoup(self.HTML, 'html.parser')
+
+    def assertSelects(self, selector, expected_ids, **kwargs):
+        el_ids = [el['id'] for el in self.soup.select(selector, **kwargs)]
+        el_ids.sort()
+        expected_ids.sort()
+        self.assertEqual(expected_ids, el_ids,
+            "Selector %s, expected [%s], got [%s]" % (
+                selector, ', '.join(expected_ids), ', '.join(el_ids)
+            )
+        )
+
+    assertSelect = assertSelects
+
+    def assertSelectMultiple(self, *tests):
+        for selector, expected_ids in tests:
+            self.assertSelect(selector, expected_ids)
+
+    def test_one_tag_one(self):
+        els = self.soup.select('title')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].name, 'title')
+        self.assertEqual(els[0].contents, ['The title'])
+
+    def test_one_tag_many(self):
+        els = self.soup.select('div')
+        self.assertEqual(len(els), 4)
+        for div in els:
+            self.assertEqual(div.name, 'div')
+
+        el = self.soup.select_one('div')
+        self.assertEqual('main', el['id'])
+
+    def test_select_one_returns_none_if_no_match(self):
+        match = self.soup.select_one('nonexistenttag')
+        self.assertEqual(None, match)
+
+
+    def test_tag_in_tag_one(self):
+        els = self.soup.select('div div')
+        self.assertSelects('div div', ['inner', 'data1'])
+
+    def test_tag_in_tag_many(self):
+        for selector in ('html div', 'html body div', 'body div'):
+            self.assertSelects(selector, ['data1', 'main', 'inner', 'footer'])
+
+
+    def test_limit(self):
+        self.assertSelects('html div', ['main'], limit=1)
+        self.assertSelects('html body div', ['inner', 'main'], limit=2)
+        self.assertSelects('body div', ['data1', 'main', 'inner', 'footer'],
+                           limit=10)
+
+    def test_tag_no_match(self):
+        self.assertEqual(len(self.soup.select('del')), 0)
+
+    def test_invalid_tag(self):
+        self.assertRaises(SyntaxError, self.soup.select, 'tag%t')
+
+    def test_select_dashed_tag_ids(self):
+        self.assertSelects('custom-dashed-tag', ['dash1', 'dash2'])
+
+    def test_select_dashed_by_id(self):
+        dashed = self.soup.select('custom-dashed-tag[id=\"dash2\"]')
+        self.assertEqual(dashed[0].name, 'custom-dashed-tag')
+        self.assertEqual(dashed[0]['id'], 'dash2')
+
+    def test_dashed_tag_text(self):
+        self.assertEqual(self.soup.select('body > custom-dashed-tag')[0].text, 'Hello there.')
+
+    def test_select_dashed_matches_find_all(self):
+        self.assertEqual(self.soup.select('custom-dashed-tag'), self.soup.find_all('custom-dashed-tag'))
+
+    def test_header_tags(self):
+        self.assertSelectMultiple(
+            ('h1', ['header1']),
+            ('h2', ['header2', 'header3']),
+        )
+
+    def test_class_one(self):
+        for selector in ('.onep', 'p.onep', 'html p.onep'):
+            els = self.soup.select(selector)
+            self.assertEqual(len(els), 1)
+            self.assertEqual(els[0].name, 'p')
+            self.assertEqual(els[0]['class'], ['onep'])
+
+    def test_class_mismatched_tag(self):
+        els = self.soup.select('div.onep')
+        self.assertEqual(len(els), 0)
+
+    def test_one_id(self):
+        for selector in ('div#inner', '#inner', 'div div#inner'):
+            self.assertSelects(selector, ['inner'])
+
+    def test_bad_id(self):
+        els = self.soup.select('#doesnotexist')
+        self.assertEqual(len(els), 0)
+
+    def test_items_in_id(self):
+        els = self.soup.select('div#inner p')
+        self.assertEqual(len(els), 3)
+        for el in els:
+            self.assertEqual(el.name, 'p')
+        self.assertEqual(els[1]['class'], ['onep'])
+        self.assertFalse(els[0].has_attr('class'))
+
+    def test_a_bunch_of_emptys(self):
+        for selector in ('div#main del', 'div#main div.oops', 'div div#main'):
+            self.assertEqual(len(self.soup.select(selector)), 0)
+
+    def test_multi_class_support(self):
+        for selector in ('.class1', 'p.class1', '.class2', 'p.class2',
+            '.class3', 'p.class3', 'html p.class2', 'div#inner .class2'):
+            self.assertSelects(selector, ['pmulti'])
+
+    def test_multi_class_selection(self):
+        for selector in ('.class1.class3', '.class3.class2',
+                         '.class1.class2.class3'):
+            self.assertSelects(selector, ['pmulti'])
+
+    def test_child_selector(self):
+        self.assertSelects('.s1 > a', ['s1a1', 's1a2'])
+        self.assertSelects('.s1 > a span', ['s1a2s1'])
+
+    def test_child_selector_id(self):
+        self.assertSelects('.s1 > a#s1a2 span', ['s1a2s1'])
+
+    def test_attribute_equals(self):
+        self.assertSelectMultiple(
+            ('p[class="onep"]', ['p1']),
+            ('p[id="p1"]', ['p1']),
+            ('[class="onep"]', ['p1']),
+            ('[id="p1"]', ['p1']),
+            ('link[rel="stylesheet"]', ['l1']),
+            ('link[type="text/css"]', ['l1']),
+            ('link[href="blah.css"]', ['l1']),
+            ('link[href="no-blah.css"]', []),
+            ('[rel="stylesheet"]', ['l1']),
+            ('[type="text/css"]', ['l1']),
+            ('[href="blah.css"]', ['l1']),
+            ('[href="no-blah.css"]', []),
+            ('p[href="no-blah.css"]', []),
+            ('[href="no-blah.css"]', []),
+        )
+
+    def test_attribute_tilde(self):
+        self.assertSelectMultiple(
+            ('p[class~="class1"]', ['pmulti']),
+            ('p[class~="class2"]', ['pmulti']),
+            ('p[class~="class3"]', ['pmulti']),
+            ('[class~="class1"]', ['pmulti']),
+            ('[class~="class2"]', ['pmulti']),
+            ('[class~="class3"]', ['pmulti']),
+            ('a[rel~="friend"]', ['bob']),
+            ('a[rel~="met"]', ['bob']),
+            ('[rel~="friend"]', ['bob']),
+            ('[rel~="met"]', ['bob']),
+        )
+
+    def test_attribute_startswith(self):
+        self.assertSelectMultiple(
+            ('[rel^="style"]', ['l1']),
+            ('link[rel^="style"]', ['l1']),
+            ('notlink[rel^="notstyle"]', []),
+            ('[rel^="notstyle"]', []),
+            ('link[rel^="notstyle"]', []),
+            ('link[href^="bla"]', ['l1']),
+            ('a[href^="http://"]', ['bob', 'me']),
+            ('[href^="http://"]', ['bob', 'me']),
+            ('[id^="p"]', ['pmulti', 'p1']),
+            ('[id^="m"]', ['me', 'main']),
+            ('div[id^="m"]', ['main']),
+            ('a[id^="m"]', ['me']),
+            ('div[data-tag^="dashed"]', ['data1'])
+        )
+
+    def test_attribute_endswith(self):
+        self.assertSelectMultiple(
+            ('[href$=".css"]', ['l1']),
+            ('link[href$=".css"]', ['l1']),
+            ('link[id$="1"]', ['l1']),
+            ('[id$="1"]', ['data1', 'l1', 'p1', 'header1', 's1a1', 's2a1', 's1a2s1', 'dash1']),
+            ('div[id$="1"]', ['data1']),
+            ('[id$="noending"]', []),
+        )
+
+    def test_attribute_contains(self):
+        self.assertSelectMultiple(
+            # From test_attribute_startswith
+            ('[rel*="style"]', ['l1']),
+            ('link[rel*="style"]', ['l1']),
+            ('notlink[rel*="notstyle"]', []),
+            ('[rel*="notstyle"]', []),
+            ('link[rel*="notstyle"]', []),
+            ('link[href*="bla"]', ['l1']),
+            ('[href*="http://"]', ['bob', 'me']),
+            ('[id*="p"]', ['pmulti', 'p1']),
+            ('div[id*="m"]', ['main']),
+            ('a[id*="m"]', ['me']),
+            # From test_attribute_endswith
+            ('[href*=".css"]', ['l1']),
+            ('link[href*=".css"]', ['l1']),
+            ('link[id*="1"]', ['l1']),
+            ('[id*="1"]', ['data1', 'l1', 'p1', 'header1', 's1a1', 's1a2', 's2a1', 's1a2s1', 'dash1']),
+            ('div[id*="1"]', ['data1']),
+            ('[id*="noending"]', []),
+            # New for this test
+            ('[href*="."]', ['bob', 'me', 'l1']),
+            ('a[href*="."]', ['bob', 'me']),
+            ('link[href*="."]', ['l1']),
+            ('div[id*="n"]', ['main', 'inner']),
+            ('div[id*="nn"]', ['inner']),
+            ('div[data-tag*="edval"]', ['data1'])
+        )
+
+    def test_attribute_exact_or_hypen(self):
+        self.assertSelectMultiple(
+            ('p[lang|="en"]', ['lang-en', 'lang-en-gb', 'lang-en-us']),
+            ('[lang|="en"]', ['lang-en', 'lang-en-gb', 'lang-en-us']),
+            ('p[lang|="fr"]', ['lang-fr']),
+            ('p[lang|="gb"]', []),
+        )
+
+    def test_attribute_exists(self):
+        self.assertSelectMultiple(
+            ('[rel]', ['l1', 'bob', 'me']),
+            ('link[rel]', ['l1']),
+            ('a[rel]', ['bob', 'me']),
+            ('[lang]', ['lang-en', 'lang-en-gb', 'lang-en-us', 'lang-fr']),
+            ('p[class]', ['p1', 'pmulti']),
+            ('[blah]', []),
+            ('p[blah]', []),
+            ('div[data-tag]', ['data1'])
+        )
+
+    def test_quoted_space_in_selector_name(self):
+        html = """<div style="display: wrong">nope</div>
+        <div style="display: right">yes</div>
+        """
+        soup = BeautifulSoup(html, 'html.parser')
+        [chosen] = soup.select('div[style="display: right"]')
+        self.assertEqual("yes", chosen.string)
+
+    def test_unsupported_pseudoclass(self):
+        self.assertRaises(
+            NotImplementedError, self.soup.select, "a:no-such-pseudoclass")
+
+        self.assertRaises(
+            SyntaxError, self.soup.select, "a:nth-of-type(a)")
+
+    def test_nth_of_type(self):
+        # Try to select first paragraph
+        els = self.soup.select('div#inner p:nth-of-type(1)')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].string, 'Some text')
+
+        # Try to select third paragraph
+        els = self.soup.select('div#inner p:nth-of-type(3)')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].string, 'Another')
+
+        # Try to select (non-existent!) fourth paragraph
+        els = self.soup.select('div#inner p:nth-of-type(4)')
+        self.assertEqual(len(els), 0)
+
+        # Zero will select no tags.
+        els = self.soup.select('div p:nth-of-type(0)')
+        self.assertEqual(len(els), 0)
+
+    def test_nth_of_type_direct_descendant(self):
+        els = self.soup.select('div#inner > p:nth-of-type(1)')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].string, 'Some text')
+
+    def test_id_child_selector_nth_of_type(self):
+        self.assertSelects('#inner > p:nth-of-type(2)', ['p1'])
+
+    def test_select_on_element(self):
+        # Other tests operate on the tree; this operates on an element
+        # within the tree.
+        inner = self.soup.find("div", id="main")
+        selected = inner.select("div")
+        # The <div id="inner"> tag was selected. The <div id="footer">
+        # tag was not.
+        self.assertSelectsIDs(selected, ['inner', 'data1'])
+
+    def test_overspecified_child_id(self):
+        self.assertSelects(".fancy #inner", ['inner'])
+        self.assertSelects(".normal #inner", [])
+
+    def test_adjacent_sibling_selector(self):
+        self.assertSelects('#p1 + h2', ['header2'])
+        self.assertSelects('#p1 + h2 + p', ['pmulti'])
+        self.assertSelects('#p1 + #header2 + .class1', ['pmulti'])
+        self.assertEqual([], self.soup.select('#p1 + p'))
+
+    def test_general_sibling_selector(self):
+        self.assertSelects('#p1 ~ h2', ['header2', 'header3'])
+        self.assertSelects('#p1 ~ #header2', ['header2'])
+        self.assertSelects('#p1 ~ h2 + a', ['me'])
+        self.assertSelects('#p1 ~ h2 + [rel="me"]', ['me'])
+        self.assertEqual([], self.soup.select('#inner ~ h2'))
+
+    def test_dangling_combinator(self):
+        self.assertRaises(SyntaxError, self.soup.select, 'h1 >')
+
+    def test_sibling_combinator_wont_select_same_tag_twice(self):
+        self.assertSelects('p[lang] ~ p', ['lang-en-gb', 'lang-en-us', 'lang-fr'])
+
+    # Test the selector grouping operator (the comma)
+    def test_multiple_select(self):
+        self.assertSelects('x, y', ['xid', 'yid'])
+
+    def test_multiple_select_with_no_space(self):
+        self.assertSelects('x,y', ['xid', 'yid'])
+
+    def test_multiple_select_with_more_space(self):
+        self.assertSelects('x,    y', ['xid', 'yid'])
+
+    def test_multiple_select_duplicated(self):
+        self.assertSelects('x, x', ['xid'])
+
+    def test_multiple_select_sibling(self):
+        self.assertSelects('x, y ~ p[lang=fr]', ['xid', 'lang-fr'])
+
+    def test_multiple_select_tag_and_direct_descendant(self):
+        self.assertSelects('x, y > z', ['xid', 'zidb'])
+
+    def test_multiple_select_direct_descendant_and_tags(self):
+        self.assertSelects('div > x, y, z', ['xid', 'yid', 'zida', 'zidb', 'zidab', 'zidac'])
+
+    def test_multiple_select_indirect_descendant(self):
+        self.assertSelects('div x,y,  z', ['xid', 'yid', 'zida', 'zidb', 'zidab', 'zidac'])
+
+    def test_invalid_multiple_select(self):
+        self.assertRaises(SyntaxError, self.soup.select, ',x, y')
+        self.assertRaises(SyntaxError, self.soup.select, 'x,,y')
+
+    def test_multiple_select_attrs(self):
+        self.assertSelects('p[lang=en], p[lang=en-gb]', ['lang-en', 'lang-en-gb'])
+
+    def test_multiple_select_ids(self):
+        self.assertSelects('x, y > z[id=zida], z[id=zidab], z[id=zidb]', ['xid', 'zidb', 'zidab'])
+
+    def test_multiple_select_nested(self):
+        self.assertSelects('body > div > x, y > z', ['xid', 'zidb'])
+
+    def test_select_duplicate_elements(self):
+        # When markup contains duplicate elements, a multiple select
+        # will find all of them.
+        markup = '<div class="c1"/><div class="c2"/><div class="c1"/>'
+        soup = BeautifulSoup(markup, 'html.parser')
+        selected = soup.select(".c1, .c2")
+        self.assertEqual(3, len(selected))
+
+        # Verify that find_all finds the same elements, though because
+        # of an implementation detail it finds them in a different
+        # order.
+        for element in soup.find_all(class_=['c1', 'c2']):
+            assert element in selected
diff --git a/libs/engineio/__init__.py b/libs/engineio/__init__.py
new file mode 100644
index 000000000..f2c5b774c
--- /dev/null
+++ b/libs/engineio/__init__.py
@@ -0,0 +1,25 @@
+import sys
+
+from .client import Client
+from .middleware import WSGIApp, Middleware
+from .server import Server
+if sys.version_info >= (3, 5):  # pragma: no cover
+    from .asyncio_server import AsyncServer
+    from .asyncio_client import AsyncClient
+    from .async_drivers.asgi import ASGIApp
+    try:
+        from .async_drivers.tornado import get_tornado_handler
+    except ImportError:
+        get_tornado_handler = None
+else:  # pragma: no cover
+    AsyncServer = None
+    AsyncClient = None
+    get_tornado_handler = None
+    ASGIApp = None
+
+__version__ = '3.11.2'
+
+__all__ = ['__version__', 'Server', 'WSGIApp', 'Middleware', 'Client']
+if AsyncServer is not None:  # pragma: no cover
+    __all__ += ['AsyncServer', 'ASGIApp', 'get_tornado_handler',
+                'AsyncClient'],
diff --git a/libs/engineio/async_drivers/__init__.py b/libs/engineio/async_drivers/__init__.py
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/libs/engineio/async_drivers/__init__.py
diff --git a/libs/engineio/async_drivers/aiohttp.py b/libs/engineio/async_drivers/aiohttp.py
new file mode 100644
index 000000000..ad6987649
--- /dev/null
+++ b/libs/engineio/async_drivers/aiohttp.py
@@ -0,0 +1,128 @@
+import asyncio
+import sys
+from urllib.parse import urlsplit
+
+from aiohttp.web import Response, WebSocketResponse
+import six
+
+
+def create_route(app, engineio_server, engineio_endpoint):
+    """This function sets up the engine.io endpoint as a route for the
+    application.
+
+    Note that both GET and POST requests must be hooked up on the engine.io
+    endpoint.
+    """
+    app.router.add_get(engineio_endpoint, engineio_server.handle_request)
+    app.router.add_post(engineio_endpoint, engineio_server.handle_request)
+    app.router.add_route('OPTIONS', engineio_endpoint,
+                         engineio_server.handle_request)
+
+
+def translate_request(request):
+    """This function takes the arguments passed to the request handler and
+    uses them to generate a WSGI compatible environ dictionary.
+    """
+    message = request._message
+    payload = request._payload
+
+    uri_parts = urlsplit(message.path)
+    environ = {
+        'wsgi.input': payload,
+        'wsgi.errors': sys.stderr,
+        'wsgi.version': (1, 0),
+        'wsgi.async': True,
+        'wsgi.multithread': False,
+        'wsgi.multiprocess': False,
+        'wsgi.run_once': False,
+        'SERVER_SOFTWARE': 'aiohttp',
+        'REQUEST_METHOD': message.method,
+        'QUERY_STRING': uri_parts.query or '',
+        'RAW_URI': message.path,
+        'SERVER_PROTOCOL': 'HTTP/%s.%s' % message.version,
+        'REMOTE_ADDR': '127.0.0.1',
+        'REMOTE_PORT': '0',
+        'SERVER_NAME': 'aiohttp',
+        'SERVER_PORT': '0',
+        'aiohttp.request': request
+    }
+
+    for hdr_name, hdr_value in message.headers.items():
+        hdr_name = hdr_name.upper()
+        if hdr_name == 'CONTENT-TYPE':
+            environ['CONTENT_TYPE'] = hdr_value
+            continue
+        elif hdr_name == 'CONTENT-LENGTH':
+            environ['CONTENT_LENGTH'] = hdr_value
+            continue
+
+        key = 'HTTP_%s' % hdr_name.replace('-', '_')
+        if key in environ:
+            hdr_value = '%s,%s' % (environ[key], hdr_value)
+
+        environ[key] = hdr_value
+
+    environ['wsgi.url_scheme'] = environ.get('HTTP_X_FORWARDED_PROTO', 'http')
+
+    path_info = uri_parts.path
+
+    environ['PATH_INFO'] = path_info
+    environ['SCRIPT_NAME'] = ''
+
+    return environ
+
+
+def make_response(status, headers, payload, environ):
+    """This function generates an appropriate response object for this async
+    mode.
+    """
+    return Response(body=payload, status=int(status.split()[0]),
+                    headers=headers)
+
+
+class WebSocket(object):  # pragma: no cover
+    """
+    This wrapper class provides a aiohttp WebSocket interface that is
+    somewhat compatible with eventlet's implementation.
+    """
+    def __init__(self, handler):
+        self.handler = handler
+        self._sock = None
+
+    async def __call__(self, environ):
+        request = environ['aiohttp.request']
+        self._sock = WebSocketResponse()
+        await self._sock.prepare(request)
+
+        self.environ = environ
+        await self.handler(self)
+        return self._sock
+
+    async def close(self):
+        await self._sock.close()
+
+    async def send(self, message):
+        if isinstance(message, bytes):
+            f = self._sock.send_bytes
+        else:
+            f = self._sock.send_str
+        if asyncio.iscoroutinefunction(f):
+            await f(message)
+        else:
+            f(message)
+
+    async def wait(self):
+        msg = await self._sock.receive()
+        if not isinstance(msg.data, six.binary_type) and \
+                not isinstance(msg.data, six.text_type):
+            raise IOError()
+        return msg.data
+
+
+_async = {
+    'asyncio': True,
+    'create_route': create_route,
+    'translate_request': translate_request,
+    'make_response': make_response,
+    'websocket': WebSocket,
+}
diff --git a/libs/engineio/async_drivers/asgi.py b/libs/engineio/async_drivers/asgi.py
new file mode 100644
index 000000000..9f14ef05f
--- /dev/null
+++ b/libs/engineio/async_drivers/asgi.py
@@ -0,0 +1,214 @@
+import os
+import sys
+
+from engineio.static_files import get_static_file
+
+
+class ASGIApp:
+    """ASGI application middleware for Engine.IO.
+
+    This middleware dispatches traffic to an Engine.IO application. It can
+    also serve a list of static files to the client, or forward unrelated
+    HTTP traffic to another ASGI application.
+
+    :param engineio_server: The Engine.IO server. Must be an instance of the
+                            ``engineio.AsyncServer`` class.
+    :param static_files: A dictionary with static file mapping rules. See the
+                         documentation for details on this argument.
+    :param other_asgi_app: A separate ASGI app that receives all other traffic.
+    :param engineio_path: The endpoint where the Engine.IO application should
+                          be installed. The default value is appropriate for
+                          most cases.
+
+    Example usage::
+
+        import engineio
+        import uvicorn
+
+        eio = engineio.AsyncServer()
+        app = engineio.ASGIApp(eio, static_files={
+            '/': {'content_type': 'text/html', 'filename': 'index.html'},
+            '/index.html': {'content_type': 'text/html',
+                            'filename': 'index.html'},
+        })
+        uvicorn.run(app, '127.0.0.1', 5000)
+    """
+    def __init__(self, engineio_server, other_asgi_app=None,
+                 static_files=None, engineio_path='engine.io'):
+        self.engineio_server = engineio_server
+        self.other_asgi_app = other_asgi_app
+        self.engineio_path = engineio_path.strip('/')
+        self.static_files = static_files or {}
+
+    async def __call__(self, scope, receive, send):
+        if scope['type'] in ['http', 'websocket'] and \
+                scope['path'].startswith('/{0}/'.format(self.engineio_path)):
+            await self.engineio_server.handle_request(scope, receive, send)
+        else:
+            static_file = get_static_file(scope['path'], self.static_files) \
+                if scope['type'] == 'http' and self.static_files else None
+            if static_file:
+                await self.serve_static_file(static_file, receive, send)
+            elif self.other_asgi_app is not None:
+                await self.other_asgi_app(scope, receive, send)
+            elif scope['type'] == 'lifespan':
+                await self.lifespan(receive, send)
+            else:
+                await self.not_found(receive, send)
+
+    async def serve_static_file(self, static_file, receive,
+                                send):  # pragma: no cover
+        event = await receive()
+        if event['type'] == 'http.request':
+            if os.path.exists(static_file['filename']):
+                with open(static_file['filename'], 'rb') as f:
+                    payload = f.read()
+                await send({'type': 'http.response.start',
+                            'status': 200,
+                            'headers': [(b'Content-Type', static_file[
+                                'content_type'].encode('utf-8'))]})
+                await send({'type': 'http.response.body',
+                            'body': payload})
+            else:
+                await self.not_found(receive, send)
+
+    async def lifespan(self, receive, send):
+        event = await receive()
+        if event['type'] == 'lifespan.startup':
+            await send({'type': 'lifespan.startup.complete'})
+        elif event['type'] == 'lifespan.shutdown':
+            await send({'type': 'lifespan.shutdown.complete'})
+
+    async def not_found(self, receive, send):
+        """Return a 404 Not Found error to the client."""
+        await send({'type': 'http.response.start',
+                    'status': 404,
+                    'headers': [(b'Content-Type', b'text/plain')]})
+        await send({'type': 'http.response.body',
+                    'body': b'Not Found'})
+
+
+async def translate_request(scope, receive, send):
+    class AwaitablePayload(object):  # pragma: no cover
+        def __init__(self, payload):
+            self.payload = payload or b''
+
+        async def read(self, length=None):
+            if length is None:
+                r = self.payload
+                self.payload = b''
+            else:
+                r = self.payload[:length]
+                self.payload = self.payload[length:]
+            return r
+
+    event = await receive()
+    payload = b''
+    if event['type'] == 'http.request':
+        payload += event.get('body') or b''
+        while event.get('more_body'):
+            event = await receive()
+            if event['type'] == 'http.request':
+                payload += event.get('body') or b''
+    elif event['type'] == 'websocket.connect':
+        await send({'type': 'websocket.accept'})
+    else:
+        return {}
+
+    raw_uri = scope['path'].encode('utf-8')
+    if 'query_string' in scope and scope['query_string']:
+        raw_uri += b'?' + scope['query_string']
+    environ = {
+        'wsgi.input': AwaitablePayload(payload),
+        'wsgi.errors': sys.stderr,
+        'wsgi.version': (1, 0),
+        'wsgi.async': True,
+        'wsgi.multithread': False,
+        'wsgi.multiprocess': False,
+        'wsgi.run_once': False,
+        'SERVER_SOFTWARE': 'asgi',
+        'REQUEST_METHOD': scope.get('method', 'GET'),
+        'PATH_INFO': scope['path'],
+        'QUERY_STRING': scope.get('query_string', b'').decode('utf-8'),
+        'RAW_URI': raw_uri.decode('utf-8'),
+        'SCRIPT_NAME': '',
+        'SERVER_PROTOCOL': 'HTTP/1.1',
+        'REMOTE_ADDR': '127.0.0.1',
+        'REMOTE_PORT': '0',
+        'SERVER_NAME': 'asgi',
+        'SERVER_PORT': '0',
+        'asgi.receive': receive,
+        'asgi.send': send,
+    }
+
+    for hdr_name, hdr_value in scope['headers']:
+        hdr_name = hdr_name.upper().decode('utf-8')
+        hdr_value = hdr_value.decode('utf-8')
+        if hdr_name == 'CONTENT-TYPE':
+            environ['CONTENT_TYPE'] = hdr_value
+            continue
+        elif hdr_name == 'CONTENT-LENGTH':
+            environ['CONTENT_LENGTH'] = hdr_value
+            continue
+
+        key = 'HTTP_%s' % hdr_name.replace('-', '_')
+        if key in environ:
+            hdr_value = '%s,%s' % (environ[key], hdr_value)
+
+        environ[key] = hdr_value
+
+    environ['wsgi.url_scheme'] = environ.get('HTTP_X_FORWARDED_PROTO', 'http')
+    return environ
+
+
+async def make_response(status, headers, payload, environ):
+    headers = [(h[0].encode('utf-8'), h[1].encode('utf-8')) for h in headers]
+    await environ['asgi.send']({'type': 'http.response.start',
+                                'status': int(status.split(' ')[0]),
+                                'headers': headers})
+    await environ['asgi.send']({'type': 'http.response.body',
+                                'body': payload})
+
+
+class WebSocket(object):  # pragma: no cover
+    """
+    This wrapper class provides an asgi WebSocket interface that is
+    somewhat compatible with eventlet's implementation.
+    """
+    def __init__(self, handler):
+        self.handler = handler
+        self.asgi_receive = None
+        self.asgi_send = None
+
+    async def __call__(self, environ):
+        self.asgi_receive = environ['asgi.receive']
+        self.asgi_send = environ['asgi.send']
+        await self.handler(self)
+
+    async def close(self):
+        await self.asgi_send({'type': 'websocket.close'})
+
+    async def send(self, message):
+        msg_bytes = None
+        msg_text = None
+        if isinstance(message, bytes):
+            msg_bytes = message
+        else:
+            msg_text = message
+        await self.asgi_send({'type': 'websocket.send',
+                              'bytes': msg_bytes,
+                              'text': msg_text})
+
+    async def wait(self):
+        event = await self.asgi_receive()
+        if event['type'] != 'websocket.receive':
+            raise IOError()
+        return event.get('bytes') or event.get('text')
+
+
+_async = {
+    'asyncio': True,
+    'translate_request': translate_request,
+    'make_response': make_response,
+    'websocket': WebSocket,
+}
diff --git a/libs/engineio/async_drivers/eventlet.py b/libs/engineio/async_drivers/eventlet.py
new file mode 100644
index 000000000..9be3797cd
--- /dev/null
+++ b/libs/engineio/async_drivers/eventlet.py
@@ -0,0 +1,30 @@
+from __future__ import absolute_import
+
+from eventlet.green.threading import Thread, Event
+from eventlet import queue
+from eventlet import sleep
+from eventlet.websocket import WebSocketWSGI as _WebSocketWSGI
+
+
+class WebSocketWSGI(_WebSocketWSGI):
+    def __init__(self, *args, **kwargs):
+        super(WebSocketWSGI, self).__init__(*args, **kwargs)
+        self._sock = None
+
+    def __call__(self, environ, start_response):
+        if 'eventlet.input' not in environ:
+            raise RuntimeError('You need to use the eventlet server. '
+                               'See the Deployment section of the '
+                               'documentation for more information.')
+        self._sock = environ['eventlet.input'].get_socket()
+        return super(WebSocketWSGI, self).__call__(environ, start_response)
+
+
+_async = {
+    'thread': Thread,
+    'queue': queue.Queue,
+    'queue_empty': queue.Empty,
+    'event': Event,
+    'websocket': WebSocketWSGI,
+    'sleep': sleep,
+}
diff --git a/libs/engineio/async_drivers/gevent.py b/libs/engineio/async_drivers/gevent.py
new file mode 100644
index 000000000..024dd0aad
--- /dev/null
+++ b/libs/engineio/async_drivers/gevent.py
@@ -0,0 +1,63 @@
+from __future__ import absolute_import
+
+import gevent
+from gevent import queue
+from gevent.event import Event
+try:
+    import geventwebsocket  # noqa
+    _websocket_available = True
+except ImportError:
+    _websocket_available = False
+
+
+class Thread(gevent.Greenlet):  # pragma: no cover
+    """
+    This wrapper class provides gevent Greenlet interface that is compatible
+    with the standard library's Thread class.
+    """
+    def __init__(self, target, args=[], kwargs={}):
+        super(Thread, self).__init__(target, *args, **kwargs)
+
+    def _run(self):
+        return self.run()
+
+
+class WebSocketWSGI(object):  # pragma: no cover
+    """
+    This wrapper class provides a gevent WebSocket interface that is
+    compatible with eventlet's implementation.
+    """
+    def __init__(self, app):
+        self.app = app
+
+    def __call__(self, environ, start_response):
+        if 'wsgi.websocket' not in environ:
+            raise RuntimeError('You need to use the gevent-websocket server. '
+                               'See the Deployment section of the '
+                               'documentation for more information.')
+        self._sock = environ['wsgi.websocket']
+        self.environ = environ
+        self.version = self._sock.version
+        self.path = self._sock.path
+        self.origin = self._sock.origin
+        self.protocol = self._sock.protocol
+        return self.app(self)
+
+    def close(self):
+        return self._sock.close()
+
+    def send(self, message):
+        return self._sock.send(message)
+
+    def wait(self):
+        return self._sock.receive()
+
+
+_async = {
+    'thread': Thread,
+    'queue': queue.JoinableQueue,
+    'queue_empty': queue.Empty,
+    'event': Event,
+    'websocket': WebSocketWSGI if _websocket_available else None,
+    'sleep': gevent.sleep,
+}
diff --git a/libs/engineio/async_drivers/gevent_uwsgi.py b/libs/engineio/async_drivers/gevent_uwsgi.py
new file mode 100644
index 000000000..07fa2a79d
--- /dev/null
+++ b/libs/engineio/async_drivers/gevent_uwsgi.py
@@ -0,0 +1,156 @@
+from __future__ import absolute_import
+
+import six
+
+import gevent
+from gevent import queue
+from gevent.event import Event
+import uwsgi
+_websocket_available = hasattr(uwsgi, 'websocket_handshake')
+
+
+class Thread(gevent.Greenlet):  # pragma: no cover
+    """
+    This wrapper class provides gevent Greenlet interface that is compatible
+    with the standard library's Thread class.
+    """
+    def __init__(self, target, args=[], kwargs={}):
+        super(Thread, self).__init__(target, *args, **kwargs)
+
+    def _run(self):
+        return self.run()
+
+
+class uWSGIWebSocket(object):  # pragma: no cover
+    """
+    This wrapper class provides a uWSGI WebSocket interface that is
+    compatible with eventlet's implementation.
+    """
+    def __init__(self, app):
+        self.app = app
+        self._sock = None
+
+    def __call__(self, environ, start_response):
+        self._sock = uwsgi.connection_fd()
+        self.environ = environ
+
+        uwsgi.websocket_handshake()
+
+        self._req_ctx = None
+        if hasattr(uwsgi, 'request_context'):
+            # uWSGI >= 2.1.x with support for api access across-greenlets
+            self._req_ctx = uwsgi.request_context()
+        else:
+            # use event and queue for sending messages
+            from gevent.event import Event
+            from gevent.queue import Queue
+            from gevent.select import select
+            self._event = Event()
+            self._send_queue = Queue()
+
+            # spawn a select greenlet
+            def select_greenlet_runner(fd, event):
+                """Sets event when data becomes available to read on fd."""
+                while True:
+                    event.set()
+                    try:
+                        select([fd], [], [])[0]
+                    except ValueError:
+                        break
+            self._select_greenlet = gevent.spawn(
+                select_greenlet_runner,
+                self._sock,
+                self._event)
+
+        self.app(self)
+
+    def close(self):
+        """Disconnects uWSGI from the client."""
+        uwsgi.disconnect()
+        if self._req_ctx is None:
+            # better kill it here in case wait() is not called again
+            self._select_greenlet.kill()
+            self._event.set()
+
+    def _send(self, msg):
+        """Transmits message either in binary or UTF-8 text mode,
+        depending on its type."""
+        if isinstance(msg, six.binary_type):
+            method = uwsgi.websocket_send_binary
+        else:
+            method = uwsgi.websocket_send
+        if self._req_ctx is not None:
+            method(msg, request_context=self._req_ctx)
+        else:
+            method(msg)
+
+    def _decode_received(self, msg):
+        """Returns either bytes or str, depending on message type."""
+        if not isinstance(msg, six.binary_type):
+            # already decoded - do nothing
+            return msg
+        # only decode from utf-8 if message is not binary data
+        type = six.byte2int(msg[0:1])
+        if type >= 48:  # no binary
+            return msg.decode('utf-8')
+        # binary message, don't try to decode
+        return msg
+
+    def send(self, msg):
+        """Queues a message for sending. Real transmission is done in
+        wait method.
+        Sends directly if uWSGI version is new enough."""
+        if self._req_ctx is not None:
+            self._send(msg)
+        else:
+            self._send_queue.put(msg)
+            self._event.set()
+
+    def wait(self):
+        """Waits and returns received messages.
+        If running in compatibility mode for older uWSGI versions,
+        it also sends messages that have been queued by send().
+        A return value of None means that connection was closed.
+        This must be called repeatedly. For uWSGI < 2.1.x it must
+        be called from the main greenlet."""
+        while True:
+            if self._req_ctx is not None:
+                try:
+                    msg = uwsgi.websocket_recv(request_context=self._req_ctx)
+                except IOError:  # connection closed
+                    return None
+                return self._decode_received(msg)
+            else:
+                # we wake up at least every 3 seconds to let uWSGI
+                # do its ping/ponging
+                event_set = self._event.wait(timeout=3)
+                if event_set:
+                    self._event.clear()
+                    # maybe there is something to send
+                    msgs = []
+                    while True:
+                        try:
+                            msgs.append(self._send_queue.get(block=False))
+                        except gevent.queue.Empty:
+                            break
+                    for msg in msgs:
+                        self._send(msg)
+                # maybe there is something to receive, if not, at least
+                # ensure uWSGI does its ping/ponging
+                try:
+                    msg = uwsgi.websocket_recv_nb()
+                except IOError:  # connection closed
+                    self._select_greenlet.kill()
+                    return None
+                if msg:  # message available
+                    return self._decode_received(msg)
+
+
+_async = {
+    'thread': Thread,
+    'queue': queue.JoinableQueue,
+    'queue_empty': queue.Empty,
+    'event': Event,
+    'websocket': uWSGIWebSocket if _websocket_available else None,
+    'sleep': gevent.sleep,
+}
diff --git a/libs/engineio/async_drivers/sanic.py b/libs/engineio/async_drivers/sanic.py
new file mode 100644
index 000000000..6929654b9
--- /dev/null
+++ b/libs/engineio/async_drivers/sanic.py
@@ -0,0 +1,144 @@
+import sys
+from urllib.parse import urlsplit
+
+from sanic.response import HTTPResponse
+try:
+    from sanic.websocket import WebSocketProtocol
+except ImportError:
+    # the installed version of sanic does not have websocket support
+    WebSocketProtocol = None
+import six
+
+
+def create_route(app, engineio_server, engineio_endpoint):
+    """This function sets up the engine.io endpoint as a route for the
+    application.
+
+    Note that both GET and POST requests must be hooked up on the engine.io
+    endpoint.
+    """
+    app.add_route(engineio_server.handle_request, engineio_endpoint,
+                  methods=['GET', 'POST', 'OPTIONS'])
+    try:
+        app.enable_websocket()
+    except AttributeError:
+        # ignore, this version does not support websocket
+        pass
+
+
+def translate_request(request):
+    """This function takes the arguments passed to the request handler and
+    uses them to generate a WSGI compatible environ dictionary.
+    """
+    class AwaitablePayload(object):
+        def __init__(self, payload):
+            self.payload = payload or b''
+
+        async def read(self, length=None):
+            if length is None:
+                r = self.payload
+                self.payload = b''
+            else:
+                r = self.payload[:length]
+                self.payload = self.payload[length:]
+            return r
+
+    uri_parts = urlsplit(request.url)
+    environ = {
+        'wsgi.input': AwaitablePayload(request.body),
+        'wsgi.errors': sys.stderr,
+        'wsgi.version': (1, 0),
+        'wsgi.async': True,
+        'wsgi.multithread': False,
+        'wsgi.multiprocess': False,
+        'wsgi.run_once': False,
+        'SERVER_SOFTWARE': 'sanic',
+        'REQUEST_METHOD': request.method,
+        'QUERY_STRING': uri_parts.query or '',
+        'RAW_URI': request.url,
+        'SERVER_PROTOCOL': 'HTTP/' + request.version,
+        'REMOTE_ADDR': '127.0.0.1',
+        'REMOTE_PORT': '0',
+        'SERVER_NAME': 'sanic',
+        'SERVER_PORT': '0',
+        'sanic.request': request
+    }
+
+    for hdr_name, hdr_value in request.headers.items():
+        hdr_name = hdr_name.upper()
+        if hdr_name == 'CONTENT-TYPE':
+            environ['CONTENT_TYPE'] = hdr_value
+            continue
+        elif hdr_name == 'CONTENT-LENGTH':
+            environ['CONTENT_LENGTH'] = hdr_value
+            continue
+
+        key = 'HTTP_%s' % hdr_name.replace('-', '_')
+        if key in environ:
+            hdr_value = '%s,%s' % (environ[key], hdr_value)
+
+        environ[key] = hdr_value
+
+    environ['wsgi.url_scheme'] = environ.get('HTTP_X_FORWARDED_PROTO', 'http')
+
+    path_info = uri_parts.path
+
+    environ['PATH_INFO'] = path_info
+    environ['SCRIPT_NAME'] = ''
+
+    return environ
+
+
+def make_response(status, headers, payload, environ):
+    """This function generates an appropriate response object for this async
+    mode.
+    """
+    headers_dict = {}
+    content_type = None
+    for h in headers:
+        if h[0].lower() == 'content-type':
+            content_type = h[1]
+        else:
+            headers_dict[h[0]] = h[1]
+    return HTTPResponse(body_bytes=payload, content_type=content_type,
+                        status=int(status.split()[0]), headers=headers_dict)
+
+
+class WebSocket(object):  # pragma: no cover
+    """
+    This wrapper class provides a sanic WebSocket interface that is
+    somewhat compatible with eventlet's implementation.
+    """
+    def __init__(self, handler):
+        self.handler = handler
+        self._sock = None
+
+    async def __call__(self, environ):
+        request = environ['sanic.request']
+        protocol = request.transport.get_protocol()
+        self._sock = await protocol.websocket_handshake(request)
+
+        self.environ = environ
+        await self.handler(self)
+
+    async def close(self):
+        await self._sock.close()
+
+    async def send(self, message):
+        await self._sock.send(message)
+
+    async def wait(self):
+        data = await self._sock.recv()
+        if not isinstance(data, six.binary_type) and \
+                not isinstance(data, six.text_type):
+            raise IOError()
+        return data
+
+
+_async = {
+    'asyncio': True,
+    'create_route': create_route,
+    'translate_request': translate_request,
+    'make_response': make_response,
+    'websocket': WebSocket if WebSocketProtocol else None,
+}
diff --git a/libs/engineio/async_drivers/threading.py b/libs/engineio/async_drivers/threading.py
new file mode 100644
index 000000000..9b5375668
--- /dev/null
+++ b/libs/engineio/async_drivers/threading.py
@@ -0,0 +1,17 @@
+from __future__ import absolute_import
+import threading
+import time
+
+try:
+    import queue
+except ImportError:  # pragma: no cover
+    import Queue as queue
+
+_async = {
+    'thread': threading.Thread,
+    'queue': queue.Queue,
+    'queue_empty': queue.Empty,
+    'event': threading.Event,
+    'websocket': None,
+    'sleep': time.sleep,
+}
diff --git a/libs/engineio/async_drivers/tornado.py b/libs/engineio/async_drivers/tornado.py
new file mode 100644
index 000000000..adfe18f5a
--- /dev/null
+++ b/libs/engineio/async_drivers/tornado.py
@@ -0,0 +1,184 @@
+import asyncio
+import sys
+from urllib.parse import urlsplit
+from .. import exceptions
+
+import tornado.web
+import tornado.websocket
+import six
+
+
+def get_tornado_handler(engineio_server):
+    class Handler(tornado.websocket.WebSocketHandler):  # pragma: no cover
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+            if isinstance(engineio_server.cors_allowed_origins,
+                          six.string_types):
+                if engineio_server.cors_allowed_origins == '*':
+                    self.allowed_origins = None
+                else:
+                    self.allowed_origins = [
+                        engineio_server.cors_allowed_origins]
+            else:
+                self.allowed_origins = engineio_server.cors_allowed_origins
+            self.receive_queue = asyncio.Queue()
+
+        async def get(self, *args, **kwargs):
+            if self.request.headers.get('Upgrade', '').lower() == 'websocket':
+                ret = super().get(*args, **kwargs)
+                if asyncio.iscoroutine(ret):
+                    await ret
+            else:
+                await engineio_server.handle_request(self)
+
+        async def open(self, *args, **kwargs):
+            # this is the handler for the websocket request
+            asyncio.ensure_future(engineio_server.handle_request(self))
+
+        async def post(self, *args, **kwargs):
+            await engineio_server.handle_request(self)
+
+        async def options(self, *args, **kwargs):
+            await engineio_server.handle_request(self)
+
+        async def on_message(self, message):
+            await self.receive_queue.put(message)
+
+        async def get_next_message(self):
+            return await self.receive_queue.get()
+
+        def on_close(self):
+            self.receive_queue.put_nowait(None)
+
+        def check_origin(self, origin):
+            if self.allowed_origins is None or origin in self.allowed_origins:
+                return True
+            return super().check_origin(origin)
+
+        def get_compression_options(self):
+            # enable compression
+            return {}
+
+    return Handler
+
+
+def translate_request(handler):
+    """This function takes the arguments passed to the request handler and
+    uses them to generate a WSGI compatible environ dictionary.
+    """
+    class AwaitablePayload(object):
+        def __init__(self, payload):
+            self.payload = payload or b''
+
+        async def read(self, length=None):
+            if length is None:
+                r = self.payload
+                self.payload = b''
+            else:
+                r = self.payload[:length]
+                self.payload = self.payload[length:]
+            return r
+
+    payload = handler.request.body
+
+    uri_parts = urlsplit(handler.request.path)
+    full_uri = handler.request.path
+    if handler.request.query:  # pragma: no cover
+        full_uri += '?' + handler.request.query
+    environ = {
+        'wsgi.input': AwaitablePayload(payload),
+        'wsgi.errors': sys.stderr,
+        'wsgi.version': (1, 0),
+        'wsgi.async': True,
+        'wsgi.multithread': False,
+        'wsgi.multiprocess': False,
+        'wsgi.run_once': False,
+        'SERVER_SOFTWARE': 'aiohttp',
+        'REQUEST_METHOD': handler.request.method,
+        'QUERY_STRING': handler.request.query or '',
+        'RAW_URI': full_uri,
+        'SERVER_PROTOCOL': 'HTTP/%s' % handler.request.version,
+        'REMOTE_ADDR': '127.0.0.1',
+        'REMOTE_PORT': '0',
+        'SERVER_NAME': 'aiohttp',
+        'SERVER_PORT': '0',
+        'tornado.handler': handler
+    }
+
+    for hdr_name, hdr_value in handler.request.headers.items():
+        hdr_name = hdr_name.upper()
+        if hdr_name == 'CONTENT-TYPE':
+            environ['CONTENT_TYPE'] = hdr_value
+            continue
+        elif hdr_name == 'CONTENT-LENGTH':
+            environ['CONTENT_LENGTH'] = hdr_value
+            continue
+
+        key = 'HTTP_%s' % hdr_name.replace('-', '_')
+        environ[key] = hdr_value
+
+    environ['wsgi.url_scheme'] = environ.get('HTTP_X_FORWARDED_PROTO', 'http')
+
+    path_info = uri_parts.path
+
+    environ['PATH_INFO'] = path_info
+    environ['SCRIPT_NAME'] = ''
+
+    return environ
+
+
+def make_response(status, headers, payload, environ):
+    """This function generates an appropriate response object for this async
+    mode.
+    """
+    tornado_handler = environ['tornado.handler']
+    try:
+        tornado_handler.set_status(int(status.split()[0]))
+    except RuntimeError:  # pragma: no cover
+        # for websocket connections Tornado does not accept a response, since
+        # it already emitted the 101 status code
+        return
+    for header, value in headers:
+        tornado_handler.set_header(header, value)
+    tornado_handler.write(payload)
+    tornado_handler.finish()
+
+
+class WebSocket(object):  # pragma: no cover
+    """
+    This wrapper class provides a tornado WebSocket interface that is
+    somewhat compatible with eventlet's implementation.
+    """
+    def __init__(self, handler):
+        self.handler = handler
+        self.tornado_handler = None
+
+    async def __call__(self, environ):
+        self.tornado_handler = environ['tornado.handler']
+        self.environ = environ
+        await self.handler(self)
+
+    async def close(self):
+        self.tornado_handler.close()
+
+    async def send(self, message):
+        try:
+            self.tornado_handler.write_message(
+                message, binary=isinstance(message, bytes))
+        except tornado.websocket.WebSocketClosedError:
+            raise exceptions.EngineIOError()
+
+    async def wait(self):
+        msg = await self.tornado_handler.get_next_message()
+        if not isinstance(msg, six.binary_type) and \
+                not isinstance(msg, six.text_type):
+            raise IOError()
+        return msg
+
+
+_async = {
+    'asyncio': True,
+    'translate_request': translate_request,
+    'make_response': make_response,
+    'websocket': WebSocket,
+}
diff --git a/libs/engineio/asyncio_client.py b/libs/engineio/asyncio_client.py
new file mode 100644
index 000000000..049b4bd95
--- /dev/null
+++ b/libs/engineio/asyncio_client.py
@@ -0,0 +1,585 @@
+import asyncio
+import ssl
+
+try:
+    import aiohttp
+except ImportError:  # pragma: no cover
+    aiohttp = None
+import six
+
+from . import client
+from . import exceptions
+from . import packet
+from . import payload
+
+
+class AsyncClient(client.Client):
+    """An Engine.IO client for asyncio.
+
+    This class implements a fully compliant Engine.IO web client with support
+    for websocket and long-polling transports, compatible with the asyncio
+    framework on Python 3.5 or newer.
+
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+    :param request_timeout: A timeout in seconds for requests. The default is
+                            5 seconds.
+    :param ssl_verify: ``True`` to verify SSL certificates, or ``False`` to
+                       skip SSL certificate verification, allowing
+                       connections to servers with self signed certificates.
+                       The default is ``True``.
+    """
+    def is_asyncio_based(self):
+        return True
+
+    async def connect(self, url, headers={}, transports=None,
+                      engineio_path='engine.io'):
+        """Connect to an Engine.IO server.
+
+        :param url: The URL of the Engine.IO server. It can include custom
+                    query string parameters if required by the server.
+        :param headers: A dictionary with custom headers to send with the
+                        connection request.
+        :param transports: The list of allowed transports. Valid transports
+                           are ``'polling'`` and ``'websocket'``. If not
+                           given, the polling transport is connected first,
+                           then an upgrade to websocket is attempted.
+        :param engineio_path: The endpoint where the Engine.IO server is
+                              installed. The default value is appropriate for
+                              most cases.
+
+        Note: this method is a coroutine.
+
+        Example usage::
+
+            eio = engineio.Client()
+            await eio.connect('http://localhost:5000')
+        """
+        if self.state != 'disconnected':
+            raise ValueError('Client is not in a disconnected state')
+        valid_transports = ['polling', 'websocket']
+        if transports is not None:
+            if isinstance(transports, six.text_type):
+                transports = [transports]
+            transports = [transport for transport in transports
+                          if transport in valid_transports]
+            if not transports:
+                raise ValueError('No valid transports provided')
+        self.transports = transports or valid_transports
+        self.queue = self.create_queue()
+        return await getattr(self, '_connect_' + self.transports[0])(
+            url, headers, engineio_path)
+
+    async def wait(self):
+        """Wait until the connection with the server ends.
+
+        Client applications can use this function to block the main thread
+        during the life of the connection.
+
+        Note: this method is a coroutine.
+        """
+        if self.read_loop_task:
+            await self.read_loop_task
+
+    async def send(self, data, binary=None):
+        """Send a message to a client.
+
+        :param data: The data to send to the client. Data can be of type
+                     ``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
+                     or ``dict``, the data will be serialized as JSON.
+        :param binary: ``True`` to send packet as binary, ``False`` to send
+                       as text. If not given, unicode (Python 2) and str
+                       (Python 3) are sent as text, and str (Python 2) and
+                       bytes (Python 3) are sent as binary.
+
+        Note: this method is a coroutine.
+        """
+        await self._send_packet(packet.Packet(packet.MESSAGE, data=data,
+                                              binary=binary))
+
+    async def disconnect(self, abort=False):
+        """Disconnect from the server.
+
+        :param abort: If set to ``True``, do not wait for background tasks
+                      associated with the connection to end.
+
+        Note: this method is a coroutine.
+        """
+        if self.state == 'connected':
+            await self._send_packet(packet.Packet(packet.CLOSE))
+            await self.queue.put(None)
+            self.state = 'disconnecting'
+            await self._trigger_event('disconnect', run_async=False)
+            if self.current_transport == 'websocket':
+                await self.ws.close()
+            if not abort:
+                await self.read_loop_task
+            self.state = 'disconnected'
+            try:
+                client.connected_clients.remove(self)
+            except ValueError:  # pragma: no cover
+                pass
+        self._reset()
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task.
+
+        This is a utility function that applications can use to start a
+        background task.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+
+        Note: this method is a coroutine.
+        """
+        return asyncio.ensure_future(target(*args, **kwargs))
+
+    async def sleep(self, seconds=0):
+        """Sleep for the requested amount of time.
+
+        Note: this method is a coroutine.
+        """
+        return await asyncio.sleep(seconds)
+
+    def create_queue(self):
+        """Create a queue object."""
+        q = asyncio.Queue()
+        q.Empty = asyncio.QueueEmpty
+        return q
+
+    def create_event(self):
+        """Create an event object."""
+        return asyncio.Event()
+
+    def _reset(self):
+        if self.http:  # pragma: no cover
+            asyncio.ensure_future(self.http.close())
+        super()._reset()
+
+    async def _connect_polling(self, url, headers, engineio_path):
+        """Establish a long-polling connection to the Engine.IO server."""
+        if aiohttp is None:  # pragma: no cover
+            self.logger.error('aiohttp not installed -- cannot make HTTP '
+                              'requests!')
+            return
+        self.base_url = self._get_engineio_url(url, engineio_path, 'polling')
+        self.logger.info('Attempting polling connection to ' + self.base_url)
+        r = await self._send_request(
+            'GET', self.base_url + self._get_url_timestamp(), headers=headers,
+            timeout=self.request_timeout)
+        if r is None:
+            self._reset()
+            raise exceptions.ConnectionError(
+                'Connection refused by the server')
+        if r.status < 200 or r.status >= 300:
+            raise exceptions.ConnectionError(
+                'Unexpected status code {} in server response'.format(
+                    r.status))
+        try:
+            p = payload.Payload(encoded_payload=await r.read())
+        except ValueError:
+            six.raise_from(exceptions.ConnectionError(
+                'Unexpected response from server'), None)
+        open_packet = p.packets[0]
+        if open_packet.packet_type != packet.OPEN:
+            raise exceptions.ConnectionError(
+                'OPEN packet not returned by server')
+        self.logger.info(
+            'Polling connection accepted with ' + str(open_packet.data))
+        self.sid = open_packet.data['sid']
+        self.upgrades = open_packet.data['upgrades']
+        self.ping_interval = open_packet.data['pingInterval'] / 1000.0
+        self.ping_timeout = open_packet.data['pingTimeout'] / 1000.0
+        self.current_transport = 'polling'
+        self.base_url += '&sid=' + self.sid
+
+        self.state = 'connected'
+        client.connected_clients.append(self)
+        await self._trigger_event('connect', run_async=False)
+
+        for pkt in p.packets[1:]:
+            await self._receive_packet(pkt)
+
+        if 'websocket' in self.upgrades and 'websocket' in self.transports:
+            # attempt to upgrade to websocket
+            if await self._connect_websocket(url, headers, engineio_path):
+                # upgrade to websocket succeeded, we're done here
+                return
+
+        self.ping_loop_task = self.start_background_task(self._ping_loop)
+        self.write_loop_task = self.start_background_task(self._write_loop)
+        self.read_loop_task = self.start_background_task(
+            self._read_loop_polling)
+
+    async def _connect_websocket(self, url, headers, engineio_path):
+        """Establish or upgrade to a WebSocket connection with the server."""
+        if aiohttp is None:  # pragma: no cover
+            self.logger.error('aiohttp package not installed')
+            return False
+        websocket_url = self._get_engineio_url(url, engineio_path,
+                                               'websocket')
+        if self.sid:
+            self.logger.info(
+                'Attempting WebSocket upgrade to ' + websocket_url)
+            upgrade = True
+            websocket_url += '&sid=' + self.sid
+        else:
+            upgrade = False
+            self.base_url = websocket_url
+            self.logger.info(
+                'Attempting WebSocket connection to ' + websocket_url)
+
+        if self.http is None or self.http.closed:  # pragma: no cover
+            self.http = aiohttp.ClientSession()
+
+        try:
+            if not self.ssl_verify:
+                ssl_context = ssl.create_default_context()
+                ssl_context.check_hostname = False
+                ssl_context.verify_mode = ssl.CERT_NONE
+                ws = await self.http.ws_connect(
+                    websocket_url + self._get_url_timestamp(),
+                    headers=headers, ssl=ssl_context)
+            else:
+                ws = await self.http.ws_connect(
+                    websocket_url + self._get_url_timestamp(),
+                    headers=headers)
+        except (aiohttp.client_exceptions.WSServerHandshakeError,
+                aiohttp.client_exceptions.ServerConnectionError):
+            if upgrade:
+                self.logger.warning(
+                    'WebSocket upgrade failed: connection error')
+                return False
+            else:
+                raise exceptions.ConnectionError('Connection error')
+        if upgrade:
+            p = packet.Packet(packet.PING, data='probe').encode(
+                always_bytes=False)
+            try:
+                await ws.send_str(p)
+            except Exception as e:  # pragma: no cover
+                self.logger.warning(
+                    'WebSocket upgrade failed: unexpected send exception: %s',
+                    str(e))
+                return False
+            try:
+                p = (await ws.receive()).data
+            except Exception as e:  # pragma: no cover
+                self.logger.warning(
+                    'WebSocket upgrade failed: unexpected recv exception: %s',
+                    str(e))
+                return False
+            pkt = packet.Packet(encoded_packet=p)
+            if pkt.packet_type != packet.PONG or pkt.data != 'probe':
+                self.logger.warning(
+                    'WebSocket upgrade failed: no PONG packet')
+                return False
+            p = packet.Packet(packet.UPGRADE).encode(always_bytes=False)
+            try:
+                await ws.send_str(p)
+            except Exception as e:  # pragma: no cover
+                self.logger.warning(
+                    'WebSocket upgrade failed: unexpected send exception: %s',
+                    str(e))
+                return False
+            self.current_transport = 'websocket'
+            self.logger.info('WebSocket upgrade was successful')
+        else:
+            try:
+                p = (await ws.receive()).data
+            except Exception as e:  # pragma: no cover
+                raise exceptions.ConnectionError(
+                    'Unexpected recv exception: ' + str(e))
+            open_packet = packet.Packet(encoded_packet=p)
+            if open_packet.packet_type != packet.OPEN:
+                raise exceptions.ConnectionError('no OPEN packet')
+            self.logger.info(
+                'WebSocket connection accepted with ' + str(open_packet.data))
+            self.sid = open_packet.data['sid']
+            self.upgrades = open_packet.data['upgrades']
+            self.ping_interval = open_packet.data['pingInterval'] / 1000.0
+            self.ping_timeout = open_packet.data['pingTimeout'] / 1000.0
+            self.current_transport = 'websocket'
+
+            self.state = 'connected'
+            client.connected_clients.append(self)
+            await self._trigger_event('connect', run_async=False)
+
+        self.ws = ws
+        self.ping_loop_task = self.start_background_task(self._ping_loop)
+        self.write_loop_task = self.start_background_task(self._write_loop)
+        self.read_loop_task = self.start_background_task(
+            self._read_loop_websocket)
+        return True
+
+    async def _receive_packet(self, pkt):
+        """Handle incoming packets from the server."""
+        packet_name = packet.packet_names[pkt.packet_type] \
+            if pkt.packet_type < len(packet.packet_names) else 'UNKNOWN'
+        self.logger.info(
+            'Received packet %s data %s', packet_name,
+            pkt.data if not isinstance(pkt.data, bytes) else '<binary>')
+        if pkt.packet_type == packet.MESSAGE:
+            await self._trigger_event('message', pkt.data, run_async=True)
+        elif pkt.packet_type == packet.PONG:
+            self.pong_received = True
+        elif pkt.packet_type == packet.CLOSE:
+            await self.disconnect(abort=True)
+        elif pkt.packet_type == packet.NOOP:
+            pass
+        else:
+            self.logger.error('Received unexpected packet of type %s',
+                              pkt.packet_type)
+
+    async def _send_packet(self, pkt):
+        """Queue a packet to be sent to the server."""
+        if self.state != 'connected':
+            return
+        await self.queue.put(pkt)
+        self.logger.info(
+            'Sending packet %s data %s',
+            packet.packet_names[pkt.packet_type],
+            pkt.data if not isinstance(pkt.data, bytes) else '<binary>')
+
+    async def _send_request(
+            self, method, url, headers=None, body=None,
+            timeout=None):  # pragma: no cover
+        if self.http is None or self.http.closed:
+            self.http = aiohttp.ClientSession()
+        http_method = getattr(self.http, method.lower())
+
+        try:
+            if not self.ssl_verify:
+                return await http_method(
+                    url, headers=headers, data=body,
+                    timeout=aiohttp.ClientTimeout(total=timeout), ssl=False)
+            else:
+                return await http_method(
+                    url, headers=headers, data=body,
+                    timeout=aiohttp.ClientTimeout(total=timeout))
+
+        except (aiohttp.ClientError, asyncio.TimeoutError) as exc:
+            self.logger.info('HTTP %s request to %s failed with error %s.',
+                             method, url, exc)
+
+    async def _trigger_event(self, event, *args, **kwargs):
+        """Invoke an event handler."""
+        run_async = kwargs.pop('run_async', False)
+        ret = None
+        if event in self.handlers:
+            if asyncio.iscoroutinefunction(self.handlers[event]) is True:
+                if run_async:
+                    return self.start_background_task(self.handlers[event],
+                                                      *args)
+                else:
+                    try:
+                        ret = await self.handlers[event](*args)
+                    except asyncio.CancelledError:  # pragma: no cover
+                        pass
+                    except:
+                        self.logger.exception(event + ' async handler error')
+                        if event == 'connect':
+                            # if connect handler raised error we reject the
+                            # connection
+                            return False
+            else:
+                if run_async:
+                    async def async_handler():
+                        return self.handlers[event](*args)
+
+                    return self.start_background_task(async_handler)
+                else:
+                    try:
+                        ret = self.handlers[event](*args)
+                    except:
+                        self.logger.exception(event + ' handler error')
+                        if event == 'connect':
+                            # if connect handler raised error we reject the
+                            # connection
+                            return False
+        return ret
+
+    async def _ping_loop(self):
+        """This background task sends a PING to the server at the requested
+        interval.
+        """
+        self.pong_received = True
+        if self.ping_loop_event is None:
+            self.ping_loop_event = self.create_event()
+        else:
+            self.ping_loop_event.clear()
+        while self.state == 'connected':
+            if not self.pong_received:
+                self.logger.info(
+                    'PONG response has not been received, aborting')
+                if self.ws:
+                    await self.ws.close()
+                await self.queue.put(None)
+                break
+            self.pong_received = False
+            await self._send_packet(packet.Packet(packet.PING))
+            try:
+                await asyncio.wait_for(self.ping_loop_event.wait(),
+                                       self.ping_interval)
+            except (asyncio.TimeoutError,
+                    asyncio.CancelledError):  # pragma: no cover
+                pass
+        self.logger.info('Exiting ping task')
+
+    async def _read_loop_polling(self):
+        """Read packets by polling the Engine.IO server."""
+        while self.state == 'connected':
+            self.logger.info(
+                'Sending polling GET request to ' + self.base_url)
+            r = await self._send_request(
+                'GET', self.base_url + self._get_url_timestamp(),
+                timeout=max(self.ping_interval, self.ping_timeout) + 5)
+            if r is None:
+                self.logger.warning(
+                    'Connection refused by the server, aborting')
+                await self.queue.put(None)
+                break
+            if r.status < 200 or r.status >= 300:
+                self.logger.warning('Unexpected status code %s in server '
+                                    'response, aborting', r.status)
+                await self.queue.put(None)
+                break
+            try:
+                p = payload.Payload(encoded_payload=await r.read())
+            except ValueError:
+                self.logger.warning(
+                    'Unexpected packet from server, aborting')
+                await self.queue.put(None)
+                break
+            for pkt in p.packets:
+                await self._receive_packet(pkt)
+
+        self.logger.info('Waiting for write loop task to end')
+        await self.write_loop_task
+        self.logger.info('Waiting for ping loop task to end')
+        if self.ping_loop_event:  # pragma: no cover
+            self.ping_loop_event.set()
+        await self.ping_loop_task
+        if self.state == 'connected':
+            await self._trigger_event('disconnect', run_async=False)
+            try:
+                client.connected_clients.remove(self)
+            except ValueError:  # pragma: no cover
+                pass
+            self._reset()
+        self.logger.info('Exiting read loop task')
+
+    async def _read_loop_websocket(self):
+        """Read packets from the Engine.IO WebSocket connection."""
+        while self.state == 'connected':
+            p = None
+            try:
+                p = (await self.ws.receive()).data
+                if p is None:  # pragma: no cover
+                    raise RuntimeError('WebSocket read returned None')
+            except aiohttp.client_exceptions.ServerDisconnectedError:
+                self.logger.info(
+                    'Read loop: WebSocket connection was closed, aborting')
+                await self.queue.put(None)
+                break
+            except Exception as e:
+                self.logger.info(
+                    'Unexpected error "%s", aborting', str(e))
+                await self.queue.put(None)
+                break
+            if isinstance(p, six.text_type):  # pragma: no cover
+                p = p.encode('utf-8')
+            pkt = packet.Packet(encoded_packet=p)
+            await self._receive_packet(pkt)
+
+        self.logger.info('Waiting for write loop task to end')
+        await self.write_loop_task
+        self.logger.info('Waiting for ping loop task to end')
+        if self.ping_loop_event:  # pragma: no cover
+            self.ping_loop_event.set()
+        await self.ping_loop_task
+        if self.state == 'connected':
+            await self._trigger_event('disconnect', run_async=False)
+            try:
+                client.connected_clients.remove(self)
+            except ValueError:  # pragma: no cover
+                pass
+            self._reset()
+        self.logger.info('Exiting read loop task')
+
+    async def _write_loop(self):
+        """This background task sends packages to the server as they are
+        pushed to the send queue.
+        """
+        while self.state == 'connected':
+            # to simplify the timeout handling, use the maximum of the
+            # ping interval and ping timeout as timeout, with an extra 5
+            # seconds grace period
+            timeout = max(self.ping_interval, self.ping_timeout) + 5
+            packets = None
+            try:
+                packets = [await asyncio.wait_for(self.queue.get(), timeout)]
+            except (self.queue.Empty, asyncio.TimeoutError,
+                    asyncio.CancelledError):
+                self.logger.error('packet queue is empty, aborting')
+                break
+            if packets == [None]:
+                self.queue.task_done()
+                packets = []
+            else:
+                while True:
+                    try:
+                        packets.append(self.queue.get_nowait())
+                    except self.queue.Empty:
+                        break
+                    if packets[-1] is None:
+                        packets = packets[:-1]
+                        self.queue.task_done()
+                        break
+            if not packets:
+                # empty packet list returned -> connection closed
+                break
+            if self.current_transport == 'polling':
+                p = payload.Payload(packets=packets)
+                r = await self._send_request(
+                    'POST', self.base_url, body=p.encode(),
+                    headers={'Content-Type': 'application/octet-stream'},
+                    timeout=self.request_timeout)
+                for pkt in packets:
+                    self.queue.task_done()
+                if r is None:
+                    self.logger.warning(
+                        'Connection refused by the server, aborting')
+                    break
+                if r.status < 200 or r.status >= 300:
+                    self.logger.warning('Unexpected status code %s in server '
+                                        'response, aborting', r.status)
+                    self._reset()
+                    break
+            else:
+                # websocket
+                try:
+                    for pkt in packets:
+                        if pkt.binary:
+                            await self.ws.send_bytes(pkt.encode(
+                                always_bytes=False))
+                        else:
+                            await self.ws.send_str(pkt.encode(
+                                always_bytes=False))
+                        self.queue.task_done()
+                except aiohttp.client_exceptions.ServerDisconnectedError:
+                    self.logger.info(
+                        'Write loop: WebSocket connection was closed, '
+                        'aborting')
+                    break
+        self.logger.info('Exiting write loop task')
diff --git a/libs/engineio/asyncio_server.py b/libs/engineio/asyncio_server.py
new file mode 100644
index 000000000..d52b556db
--- /dev/null
+++ b/libs/engineio/asyncio_server.py
@@ -0,0 +1,472 @@
+import asyncio
+
+import six
+from six.moves import urllib
+
+from . import exceptions
+from . import packet
+from . import server
+from . import asyncio_socket
+
+
+class AsyncServer(server.Server):
+    """An Engine.IO server for asyncio.
+
+    This class implements a fully compliant Engine.IO web server with support
+    for websocket and long-polling transports, compatible with the asyncio
+    framework on Python 3.5 or newer.
+
+    :param async_mode: The asynchronous model to use. See the Deployment
+                       section in the documentation for a description of the
+                       available options. Valid async modes are "aiohttp",
+                       "sanic", "tornado" and "asgi". If this argument is not
+                       given, "aiohttp" is tried first, followed by "sanic",
+                       "tornado", and finally "asgi". The first async mode that
+                       has all its dependencies installed is the one that is
+                       chosen.
+    :param ping_timeout: The time in seconds that the client waits for the
+                         server to respond before disconnecting.
+    :param ping_interval: The interval in seconds at which the client pings
+                          the server. The default is 25 seconds. For advanced
+                          control, a two element tuple can be given, where
+                          the first number is the ping interval and the second
+                          is a grace period added by the server. The default
+                          grace period is 5 seconds.
+    :param max_http_buffer_size: The maximum size of a message when using the
+                                 polling transport.
+    :param allow_upgrades: Whether to allow transport upgrades or not.
+    :param http_compression: Whether to compress packages when using the
+                             polling transport.
+    :param compression_threshold: Only compress messages when their byte size
+                                  is greater than this value.
+    :param cookie: Name of the HTTP cookie that contains the client session
+                   id. If set to ``None``, a cookie is not sent to the client.
+    :param cors_allowed_origins: Origin or list of origins that are allowed to
+                                 connect to this server. Only the same origin
+                                 is allowed by default. Set this argument to
+                                 ``'*'`` to allow all origins, or to ``[]`` to
+                                 disable CORS handling.
+    :param cors_credentials: Whether credentials (cookies, authentication) are
+                             allowed in requests to this server.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+    :param async_handlers: If set to ``True``, run message event handlers in
+                           non-blocking threads. To run handlers synchronously,
+                           set to ``False``. The default is ``True``.
+    :param kwargs: Reserved for future extensions, any additional parameters
+                   given as keyword arguments will be silently ignored.
+    """
+    def is_asyncio_based(self):
+        return True
+
+    def async_modes(self):
+        return ['aiohttp', 'sanic', 'tornado', 'asgi']
+
+    def attach(self, app, engineio_path='engine.io'):
+        """Attach the Engine.IO server to an application."""
+        engineio_path = engineio_path.strip('/')
+        self._async['create_route'](app, self, '/{}/'.format(engineio_path))
+
+    async def send(self, sid, data, binary=None):
+        """Send a message to a client.
+
+        :param sid: The session id of the recipient client.
+        :param data: The data to send to the client. Data can be of type
+                     ``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
+                     or ``dict``, the data will be serialized as JSON.
+        :param binary: ``True`` to send packet as binary, ``False`` to send
+                       as text. If not given, unicode (Python 2) and str
+                       (Python 3) are sent as text, and str (Python 2) and
+                       bytes (Python 3) are sent as binary.
+
+        Note: this method is a coroutine.
+        """
+        try:
+            socket = self._get_socket(sid)
+        except KeyError:
+            # the socket is not available
+            self.logger.warning('Cannot send to sid %s', sid)
+            return
+        await socket.send(packet.Packet(packet.MESSAGE, data=data,
+                                        binary=binary))
+
+    async def get_session(self, sid):
+        """Return the user session for a client.
+
+        :param sid: The session id of the client.
+
+        The return value is a dictionary. Modifications made to this
+        dictionary are not guaranteed to be preserved. If you want to modify
+        the user session, use the ``session`` context manager instead.
+        """
+        socket = self._get_socket(sid)
+        return socket.session
+
+    async def save_session(self, sid, session):
+        """Store the user session for a client.
+
+        :param sid: The session id of the client.
+        :param session: The session dictionary.
+        """
+        socket = self._get_socket(sid)
+        socket.session = session
+
+    def session(self, sid):
+        """Return the user session for a client with context manager syntax.
+
+        :param sid: The session id of the client.
+
+        This is a context manager that returns the user session dictionary for
+        the client. Any changes that are made to this dictionary inside the
+        context manager block are saved back to the session. Example usage::
+
+            @eio.on('connect')
+            def on_connect(sid, environ):
+                username = authenticate_user(environ)
+                if not username:
+                    return False
+                with eio.session(sid) as session:
+                    session['username'] = username
+
+            @eio.on('message')
+            def on_message(sid, msg):
+                async with eio.session(sid) as session:
+                    print('received message from ', session['username'])
+        """
+        class _session_context_manager(object):
+            def __init__(self, server, sid):
+                self.server = server
+                self.sid = sid
+                self.session = None
+
+            async def __aenter__(self):
+                self.session = await self.server.get_session(sid)
+                return self.session
+
+            async def __aexit__(self, *args):
+                await self.server.save_session(sid, self.session)
+
+        return _session_context_manager(self, sid)
+
+    async def disconnect(self, sid=None):
+        """Disconnect a client.
+
+        :param sid: The session id of the client to close. If this parameter
+                    is not given, then all clients are closed.
+
+        Note: this method is a coroutine.
+        """
+        if sid is not None:
+            try:
+                socket = self._get_socket(sid)
+            except KeyError:  # pragma: no cover
+                # the socket was already closed or gone
+                pass
+            else:
+                await socket.close()
+                if sid in self.sockets:  # pragma: no cover
+                    del self.sockets[sid]
+        else:
+            await asyncio.wait([client.close()
+                                for client in six.itervalues(self.sockets)])
+            self.sockets = {}
+
+    async def handle_request(self, *args, **kwargs):
+        """Handle an HTTP request from the client.
+
+        This is the entry point of the Engine.IO application. This function
+        returns the HTTP response to deliver to the client.
+
+        Note: this method is a coroutine.
+        """
+        translate_request = self._async['translate_request']
+        if asyncio.iscoroutinefunction(translate_request):
+            environ = await translate_request(*args, **kwargs)
+        else:
+            environ = translate_request(*args, **kwargs)
+
+        if self.cors_allowed_origins != []:
+            # Validate the origin header if present
+            # This is important for WebSocket more than for HTTP, since
+            # browsers only apply CORS controls to HTTP.
+            origin = environ.get('HTTP_ORIGIN')
+            if origin:
+                allowed_origins = self._cors_allowed_origins(environ)
+                if allowed_origins is not None and origin not in \
+                        allowed_origins:
+                    self.logger.info(origin + ' is not an accepted origin.')
+                    r = self._bad_request()
+                    make_response = self._async['make_response']
+                    if asyncio.iscoroutinefunction(make_response):
+                        response = await make_response(
+                            r['status'], r['headers'], r['response'], environ)
+                    else:
+                        response = make_response(r['status'], r['headers'],
+                                                 r['response'], environ)
+                    return response
+
+        method = environ['REQUEST_METHOD']
+        query = urllib.parse.parse_qs(environ.get('QUERY_STRING', ''))
+
+        sid = query['sid'][0] if 'sid' in query else None
+        b64 = False
+        jsonp = False
+        jsonp_index = None
+
+        if 'b64' in query:
+            if query['b64'][0] == "1" or query['b64'][0].lower() == "true":
+                b64 = True
+        if 'j' in query:
+            jsonp = True
+            try:
+                jsonp_index = int(query['j'][0])
+            except (ValueError, KeyError, IndexError):
+                # Invalid JSONP index number
+                pass
+
+        if jsonp and jsonp_index is None:
+            self.logger.warning('Invalid JSONP index number')
+            r = self._bad_request()
+        elif method == 'GET':
+            if sid is None:
+                transport = query.get('transport', ['polling'])[0]
+                if transport != 'polling' and transport != 'websocket':
+                    self.logger.warning('Invalid transport %s', transport)
+                    r = self._bad_request()
+                else:
+                    r = await self._handle_connect(environ, transport,
+                                                   b64, jsonp_index)
+            else:
+                if sid not in self.sockets:
+                    self.logger.warning('Invalid session %s', sid)
+                    r = self._bad_request()
+                else:
+                    socket = self._get_socket(sid)
+                    try:
+                        packets = await socket.handle_get_request(environ)
+                        if isinstance(packets, list):
+                            r = self._ok(packets, b64=b64,
+                                         jsonp_index=jsonp_index)
+                        else:
+                            r = packets
+                    except exceptions.EngineIOError:
+                        if sid in self.sockets:  # pragma: no cover
+                            await self.disconnect(sid)
+                        r = self._bad_request()
+                    if sid in self.sockets and self.sockets[sid].closed:
+                        del self.sockets[sid]
+        elif method == 'POST':
+            if sid is None or sid not in self.sockets:
+                self.logger.warning('Invalid session %s', sid)
+                r = self._bad_request()
+            else:
+                socket = self._get_socket(sid)
+                try:
+                    await socket.handle_post_request(environ)
+                    r = self._ok(jsonp_index=jsonp_index)
+                except exceptions.EngineIOError:
+                    if sid in self.sockets:  # pragma: no cover
+                        await self.disconnect(sid)
+                    r = self._bad_request()
+                except:  # pragma: no cover
+                    # for any other unexpected errors, we log the error
+                    # and keep going
+                    self.logger.exception('post request handler error')
+                    r = self._ok(jsonp_index=jsonp_index)
+        elif method == 'OPTIONS':
+            r = self._ok()
+        else:
+            self.logger.warning('Method %s not supported', method)
+            r = self._method_not_found()
+        if not isinstance(r, dict):
+            return r
+        if self.http_compression and \
+                len(r['response']) >= self.compression_threshold:
+            encodings = [e.split(';')[0].strip() for e in
+                         environ.get('HTTP_ACCEPT_ENCODING', '').split(',')]
+            for encoding in encodings:
+                if encoding in self.compression_methods:
+                    r['response'] = \
+                        getattr(self, '_' + encoding)(r['response'])
+                    r['headers'] += [('Content-Encoding', encoding)]
+                    break
+        cors_headers = self._cors_headers(environ)
+        make_response = self._async['make_response']
+        if asyncio.iscoroutinefunction(make_response):
+            response = await make_response(r['status'],
+                                           r['headers'] + cors_headers,
+                                           r['response'], environ)
+        else:
+            response = make_response(r['status'], r['headers'] + cors_headers,
+                                     r['response'], environ)
+        return response
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        The return value is a ``asyncio.Task`` object.
+        """
+        return asyncio.ensure_future(target(*args, **kwargs))
+
+    async def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+
+        Note: this method is a coroutine.
+        """
+        return await asyncio.sleep(seconds)
+
+    def create_queue(self, *args, **kwargs):
+        """Create a queue object using the appropriate async model.
+
+        This is a utility function that applications can use to create a queue
+        without having to worry about using the correct call for the selected
+        async mode. For asyncio based async modes, this returns an instance of
+        ``asyncio.Queue``.
+        """
+        return asyncio.Queue(*args, **kwargs)
+
+    def get_queue_empty_exception(self):
+        """Return the queue empty exception for the appropriate async model.
+
+        This is a utility function that applications can use to work with a
+        queue without having to worry about using the correct call for the
+        selected async mode. For asyncio based async modes, this returns an
+        instance of ``asyncio.QueueEmpty``.
+        """
+        return asyncio.QueueEmpty
+
+    def create_event(self, *args, **kwargs):
+        """Create an event object using the appropriate async model.
+
+        This is a utility function that applications can use to create an
+        event without having to worry about using the correct call for the
+        selected async mode. For asyncio based async modes, this returns
+        an instance of ``asyncio.Event``.
+        """
+        return asyncio.Event(*args, **kwargs)
+
+    async def _handle_connect(self, environ, transport, b64=False,
+                              jsonp_index=None):
+        """Handle a client connection request."""
+        if self.start_service_task:
+            # start the service task to monitor connected clients
+            self.start_service_task = False
+            self.start_background_task(self._service_task)
+
+        sid = self._generate_id()
+        s = asyncio_socket.AsyncSocket(self, sid)
+        self.sockets[sid] = s
+
+        pkt = packet.Packet(
+            packet.OPEN, {'sid': sid,
+                          'upgrades': self._upgrades(sid, transport),
+                          'pingTimeout': int(self.ping_timeout * 1000),
+                          'pingInterval': int(self.ping_interval * 1000)})
+        await s.send(pkt)
+
+        ret = await self._trigger_event('connect', sid, environ,
+                                        run_async=False)
+        if ret is False:
+            del self.sockets[sid]
+            self.logger.warning('Application rejected connection')
+            return self._unauthorized()
+
+        if transport == 'websocket':
+            ret = await s.handle_get_request(environ)
+            if s.closed:
+                # websocket connection ended, so we are done
+                del self.sockets[sid]
+            return ret
+        else:
+            s.connected = True
+            headers = None
+            if self.cookie:
+                headers = [('Set-Cookie', self.cookie + '=' + sid)]
+            try:
+                return self._ok(await s.poll(), headers=headers, b64=b64,
+                                jsonp_index=jsonp_index)
+            except exceptions.QueueEmpty:
+                return self._bad_request()
+
+    async def _trigger_event(self, event, *args, **kwargs):
+        """Invoke an event handler."""
+        run_async = kwargs.pop('run_async', False)
+        ret = None
+        if event in self.handlers:
+            if asyncio.iscoroutinefunction(self.handlers[event]) is True:
+                if run_async:
+                    return self.start_background_task(self.handlers[event],
+                                                      *args)
+                else:
+                    try:
+                        ret = await self.handlers[event](*args)
+                    except asyncio.CancelledError:  # pragma: no cover
+                        pass
+                    except:
+                        self.logger.exception(event + ' async handler error')
+                        if event == 'connect':
+                            # if connect handler raised error we reject the
+                            # connection
+                            return False
+            else:
+                if run_async:
+                    async def async_handler():
+                        return self.handlers[event](*args)
+
+                    return self.start_background_task(async_handler)
+                else:
+                    try:
+                        ret = self.handlers[event](*args)
+                    except:
+                        self.logger.exception(event + ' handler error')
+                        if event == 'connect':
+                            # if connect handler raised error we reject the
+                            # connection
+                            return False
+        return ret
+
+    async def _service_task(self):  # pragma: no cover
+        """Monitor connected clients and clean up those that time out."""
+        while True:
+            if len(self.sockets) == 0:
+                # nothing to do
+                await self.sleep(self.ping_timeout)
+                continue
+
+            # go through the entire client list in a ping interval cycle
+            sleep_interval = self.ping_timeout / len(self.sockets)
+
+            try:
+                # iterate over the current clients
+                for socket in self.sockets.copy().values():
+                    if not socket.closing and not socket.closed:
+                        await socket.check_ping_timeout()
+                    await self.sleep(sleep_interval)
+            except (SystemExit, KeyboardInterrupt, asyncio.CancelledError):
+                self.logger.info('service task canceled')
+                break
+            except:
+                if asyncio.get_event_loop().is_closed():
+                    self.logger.info('event loop is closed, exiting service '
+                                     'task')
+                    break
+
+                # an unexpected exception has occurred, log it and continue
+                self.logger.exception('service task exception')
diff --git a/libs/engineio/asyncio_socket.py b/libs/engineio/asyncio_socket.py
new file mode 100644
index 000000000..7057a6cc3
--- /dev/null
+++ b/libs/engineio/asyncio_socket.py
@@ -0,0 +1,236 @@
+import asyncio
+import six
+import sys
+import time
+
+from . import exceptions
+from . import packet
+from . import payload
+from . import socket
+
+
+class AsyncSocket(socket.Socket):
+    async def poll(self):
+        """Wait for packets to send to the client."""
+        try:
+            packets = [await asyncio.wait_for(self.queue.get(),
+                                              self.server.ping_timeout)]
+            self.queue.task_done()
+        except (asyncio.TimeoutError, asyncio.CancelledError):
+            raise exceptions.QueueEmpty()
+        if packets == [None]:
+            return []
+        try:
+            packets.append(self.queue.get_nowait())
+            self.queue.task_done()
+        except asyncio.QueueEmpty:
+            pass
+        return packets
+
+    async def receive(self, pkt):
+        """Receive packet from the client."""
+        self.server.logger.info('%s: Received packet %s data %s',
+                                self.sid, packet.packet_names[pkt.packet_type],
+                                pkt.data if not isinstance(pkt.data, bytes)
+                                else '<binary>')
+        if pkt.packet_type == packet.PING:
+            self.last_ping = time.time()
+            await self.send(packet.Packet(packet.PONG, pkt.data))
+        elif pkt.packet_type == packet.MESSAGE:
+            await self.server._trigger_event(
+                'message', self.sid, pkt.data,
+                run_async=self.server.async_handlers)
+        elif pkt.packet_type == packet.UPGRADE:
+            await self.send(packet.Packet(packet.NOOP))
+        elif pkt.packet_type == packet.CLOSE:
+            await self.close(wait=False, abort=True)
+        else:
+            raise exceptions.UnknownPacketError()
+
+    async def check_ping_timeout(self):
+        """Make sure the client is still sending pings.
+
+        This helps detect disconnections for long-polling clients.
+        """
+        if self.closed:
+            raise exceptions.SocketIsClosedError()
+        if time.time() - self.last_ping > self.server.ping_interval + \
+                self.server.ping_interval_grace_period:
+            self.server.logger.info('%s: Client is gone, closing socket',
+                                    self.sid)
+            # Passing abort=False here will cause close() to write a
+            # CLOSE packet. This has the effect of updating half-open sockets
+            # to their correct state of disconnected
+            await self.close(wait=False, abort=False)
+            return False
+        return True
+
+    async def send(self, pkt):
+        """Send a packet to the client."""
+        if not await self.check_ping_timeout():
+            return
+        if self.upgrading:
+            self.packet_backlog.append(pkt)
+        else:
+            await self.queue.put(pkt)
+        self.server.logger.info('%s: Sending packet %s data %s',
+                                self.sid, packet.packet_names[pkt.packet_type],
+                                pkt.data if not isinstance(pkt.data, bytes)
+                                else '<binary>')
+
+    async def handle_get_request(self, environ):
+        """Handle a long-polling GET request from the client."""
+        connections = [
+            s.strip()
+            for s in environ.get('HTTP_CONNECTION', '').lower().split(',')]
+        transport = environ.get('HTTP_UPGRADE', '').lower()
+        if 'upgrade' in connections and transport in self.upgrade_protocols:
+            self.server.logger.info('%s: Received request to upgrade to %s',
+                                    self.sid, transport)
+            return await getattr(self, '_upgrade_' + transport)(environ)
+        try:
+            packets = await self.poll()
+        except exceptions.QueueEmpty:
+            exc = sys.exc_info()
+            await self.close(wait=False)
+            six.reraise(*exc)
+        return packets
+
+    async def handle_post_request(self, environ):
+        """Handle a long-polling POST request from the client."""
+        length = int(environ.get('CONTENT_LENGTH', '0'))
+        if length > self.server.max_http_buffer_size:
+            raise exceptions.ContentTooLongError()
+        else:
+            body = await environ['wsgi.input'].read(length)
+            p = payload.Payload(encoded_payload=body)
+            for pkt in p.packets:
+                await self.receive(pkt)
+
+    async def close(self, wait=True, abort=False):
+        """Close the socket connection."""
+        if not self.closed and not self.closing:
+            self.closing = True
+            await self.server._trigger_event('disconnect', self.sid)
+            if not abort:
+                await self.send(packet.Packet(packet.CLOSE))
+            self.closed = True
+            if wait:
+                await self.queue.join()
+
+    async def _upgrade_websocket(self, environ):
+        """Upgrade the connection from polling to websocket."""
+        if self.upgraded:
+            raise IOError('Socket has been upgraded already')
+        if self.server._async['websocket'] is None:
+            # the selected async mode does not support websocket
+            return self.server._bad_request()
+        ws = self.server._async['websocket'](self._websocket_handler)
+        return await ws(environ)
+
+    async def _websocket_handler(self, ws):
+        """Engine.IO handler for websocket transport."""
+        if self.connected:
+            # the socket was already connected, so this is an upgrade
+            self.upgrading = True  # hold packet sends during the upgrade
+
+            try:
+                pkt = await ws.wait()
+            except IOError:  # pragma: no cover
+                return
+            decoded_pkt = packet.Packet(encoded_packet=pkt)
+            if decoded_pkt.packet_type != packet.PING or \
+                    decoded_pkt.data != 'probe':
+                self.server.logger.info(
+                    '%s: Failed websocket upgrade, no PING packet', self.sid)
+                return
+            await ws.send(packet.Packet(
+                packet.PONG,
+                data=six.text_type('probe')).encode(always_bytes=False))
+            await self.queue.put(packet.Packet(packet.NOOP))  # end poll
+
+            try:
+                pkt = await ws.wait()
+            except IOError:  # pragma: no cover
+                return
+            decoded_pkt = packet.Packet(encoded_packet=pkt)
+            if decoded_pkt.packet_type != packet.UPGRADE:
+                self.upgraded = False
+                self.server.logger.info(
+                    ('%s: Failed websocket upgrade, expected UPGRADE packet, '
+                     'received %s instead.'),
+                    self.sid, pkt)
+                return
+            self.upgraded = True
+
+            # flush any packets that were sent during the upgrade
+            for pkt in self.packet_backlog:
+                await self.queue.put(pkt)
+            self.packet_backlog = []
+            self.upgrading = False
+        else:
+            self.connected = True
+            self.upgraded = True
+
+        # start separate writer thread
+        async def writer():
+            while True:
+                packets = None
+                try:
+                    packets = await self.poll()
+                except exceptions.QueueEmpty:
+                    break
+                if not packets:
+                    # empty packet list returned -> connection closed
+                    break
+                try:
+                    for pkt in packets:
+                        await ws.send(pkt.encode(always_bytes=False))
+                except:
+                    break
+        writer_task = asyncio.ensure_future(writer())
+
+        self.server.logger.info(
+            '%s: Upgrade to websocket successful', self.sid)
+
+        while True:
+            p = None
+            wait_task = asyncio.ensure_future(ws.wait())
+            try:
+                p = await asyncio.wait_for(wait_task, self.server.ping_timeout)
+            except asyncio.CancelledError:  # pragma: no cover
+                # there is a bug (https://bugs.python.org/issue30508) in
+                # asyncio that causes a "Task exception never retrieved" error
+                # to appear when wait_task raises an exception before it gets
+                # cancelled. Calling wait_task.exception() prevents the error
+                # from being issued in Python 3.6, but causes other errors in
+                # other versions, so we run it with all errors suppressed and
+                # hope for the best.
+                try:
+                    wait_task.exception()
+                except:
+                    pass
+                break
+            except:
+                break
+            if p is None:
+                # connection closed by client
+                break
+            if isinstance(p, six.text_type):  # pragma: no cover
+                p = p.encode('utf-8')
+            pkt = packet.Packet(encoded_packet=p)
+            try:
+                await self.receive(pkt)
+            except exceptions.UnknownPacketError:  # pragma: no cover
+                pass
+            except exceptions.SocketIsClosedError:  # pragma: no cover
+                self.server.logger.info('Receive error -- socket is closed')
+                break
+            except:  # pragma: no cover
+                # if we get an unexpected exception we log the error and exit
+                # the connection properly
+                self.server.logger.exception('Unknown receive error')
+
+        await self.queue.put(None)  # unlock the writer task so it can exit
+        await asyncio.wait_for(writer_task, timeout=None)
+        await self.close(wait=False, abort=True)
diff --git a/libs/engineio/client.py b/libs/engineio/client.py
new file mode 100644
index 000000000..b5ab50377
--- /dev/null
+++ b/libs/engineio/client.py
@@ -0,0 +1,680 @@
+import logging
+try:
+    import queue
+except ImportError:  # pragma: no cover
+    import Queue as queue
+import signal
+import ssl
+import threading
+import time
+
+import six
+from six.moves import urllib
+try:
+    import requests
+except ImportError:  # pragma: no cover
+    requests = None
+try:
+    import websocket
+except ImportError:  # pragma: no cover
+    websocket = None
+from . import exceptions
+from . import packet
+from . import payload
+
+default_logger = logging.getLogger('engineio.client')
+connected_clients = []
+
+if six.PY2:  # pragma: no cover
+    ConnectionError = OSError
+
+
+def signal_handler(sig, frame):
+    """SIGINT handler.
+
+    Disconnect all active clients and then invoke the original signal handler.
+    """
+    for client in connected_clients[:]:
+        if client.is_asyncio_based():
+            client.start_background_task(client.disconnect, abort=True)
+        else:
+            client.disconnect(abort=True)
+    if callable(original_signal_handler):
+        return original_signal_handler(sig, frame)
+    else:  # pragma: no cover
+        # Handle case where no original SIGINT handler was present.
+        return signal.default_int_handler(sig, frame)
+
+
+original_signal_handler = None
+
+
+class Client(object):
+    """An Engine.IO client.
+
+    This class implements a fully compliant Engine.IO web client with support
+    for websocket and long-polling transports.
+
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+    :param request_timeout: A timeout in seconds for requests. The default is
+                            5 seconds.
+    :param ssl_verify: ``True`` to verify SSL certificates, or ``False`` to
+                       skip SSL certificate verification, allowing
+                       connections to servers with self signed certificates.
+                       The default is ``True``.
+    """
+    event_names = ['connect', 'disconnect', 'message']
+
+    def __init__(self,
+                 logger=False,
+                 json=None,
+                 request_timeout=5,
+                 ssl_verify=True):
+        global original_signal_handler
+        if original_signal_handler is None:
+            original_signal_handler = signal.signal(signal.SIGINT,
+                                                    signal_handler)
+        self.handlers = {}
+        self.base_url = None
+        self.transports = None
+        self.current_transport = None
+        self.sid = None
+        self.upgrades = None
+        self.ping_interval = None
+        self.ping_timeout = None
+        self.pong_received = True
+        self.http = None
+        self.ws = None
+        self.read_loop_task = None
+        self.write_loop_task = None
+        self.ping_loop_task = None
+        self.ping_loop_event = None
+        self.queue = None
+        self.state = 'disconnected'
+        self.ssl_verify = ssl_verify
+
+        if json is not None:
+            packet.Packet.json = json
+        if not isinstance(logger, bool):
+            self.logger = logger
+        else:
+            self.logger = default_logger
+            if not logging.root.handlers and \
+                    self.logger.level == logging.NOTSET:
+                if logger:
+                    self.logger.setLevel(logging.INFO)
+                else:
+                    self.logger.setLevel(logging.ERROR)
+                self.logger.addHandler(logging.StreamHandler())
+
+        self.request_timeout = request_timeout
+
+    def is_asyncio_based(self):
+        return False
+
+    def on(self, event, handler=None):
+        """Register an event handler.
+
+        :param event: The event name. Can be ``'connect'``, ``'message'`` or
+                      ``'disconnect'``.
+        :param handler: The function that should be invoked to handle the
+                        event. When this parameter is not given, the method
+                        acts as a decorator for the handler function.
+
+        Example usage::
+
+            # as a decorator:
+            @eio.on('connect')
+            def connect_handler():
+                print('Connection request')
+
+            # as a method:
+            def message_handler(msg):
+                print('Received message: ', msg)
+                eio.send('response')
+            eio.on('message', message_handler)
+        """
+        if event not in self.event_names:
+            raise ValueError('Invalid event')
+
+        def set_handler(handler):
+            self.handlers[event] = handler
+            return handler
+
+        if handler is None:
+            return set_handler
+        set_handler(handler)
+
+    def connect(self, url, headers={}, transports=None,
+                engineio_path='engine.io'):
+        """Connect to an Engine.IO server.
+
+        :param url: The URL of the Engine.IO server. It can include custom
+                    query string parameters if required by the server.
+        :param headers: A dictionary with custom headers to send with the
+                        connection request.
+        :param transports: The list of allowed transports. Valid transports
+                           are ``'polling'`` and ``'websocket'``. If not
+                           given, the polling transport is connected first,
+                           then an upgrade to websocket is attempted.
+        :param engineio_path: The endpoint where the Engine.IO server is
+                              installed. The default value is appropriate for
+                              most cases.
+
+        Example usage::
+
+            eio = engineio.Client()
+            eio.connect('http://localhost:5000')
+        """
+        if self.state != 'disconnected':
+            raise ValueError('Client is not in a disconnected state')
+        valid_transports = ['polling', 'websocket']
+        if transports is not None:
+            if isinstance(transports, six.string_types):
+                transports = [transports]
+            transports = [transport for transport in transports
+                          if transport in valid_transports]
+            if not transports:
+                raise ValueError('No valid transports provided')
+        self.transports = transports or valid_transports
+        self.queue = self.create_queue()
+        return getattr(self, '_connect_' + self.transports[0])(
+            url, headers, engineio_path)
+
+    def wait(self):
+        """Wait until the connection with the server ends.
+
+        Client applications can use this function to block the main thread
+        during the life of the connection.
+        """
+        if self.read_loop_task:
+            self.read_loop_task.join()
+
+    def send(self, data, binary=None):
+        """Send a message to a client.
+
+        :param data: The data to send to the client. Data can be of type
+                     ``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
+                     or ``dict``, the data will be serialized as JSON.
+        :param binary: ``True`` to send packet as binary, ``False`` to send
+                       as text. If not given, unicode (Python 2) and str
+                       (Python 3) are sent as text, and str (Python 2) and
+                       bytes (Python 3) are sent as binary.
+        """
+        self._send_packet(packet.Packet(packet.MESSAGE, data=data,
+                                        binary=binary))
+
+    def disconnect(self, abort=False):
+        """Disconnect from the server.
+
+        :param abort: If set to ``True``, do not wait for background tasks
+                      associated with the connection to end.
+        """
+        if self.state == 'connected':
+            self._send_packet(packet.Packet(packet.CLOSE))
+            self.queue.put(None)
+            self.state = 'disconnecting'
+            self._trigger_event('disconnect', run_async=False)
+            if self.current_transport == 'websocket':
+                self.ws.close()
+            if not abort:
+                self.read_loop_task.join()
+            self.state = 'disconnected'
+            try:
+                connected_clients.remove(self)
+            except ValueError:  # pragma: no cover
+                pass
+        self._reset()
+
+    def transport(self):
+        """Return the name of the transport currently in use.
+
+        The possible values returned by this function are ``'polling'`` and
+        ``'websocket'``.
+        """
+        return self.current_transport
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task.
+
+        This is a utility function that applications can use to start a
+        background task.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+        """
+        th = threading.Thread(target=target, args=args, kwargs=kwargs)
+        th.start()
+        return th
+
+    def sleep(self, seconds=0):
+        """Sleep for the requested amount of time."""
+        return time.sleep(seconds)
+
+    def create_queue(self, *args, **kwargs):
+        """Create a queue object."""
+        q = queue.Queue(*args, **kwargs)
+        q.Empty = queue.Empty
+        return q
+
+    def create_event(self, *args, **kwargs):
+        """Create an event object."""
+        return threading.Event(*args, **kwargs)
+
+    def _reset(self):
+        self.state = 'disconnected'
+        self.sid = None
+
+    def _connect_polling(self, url, headers, engineio_path):
+        """Establish a long-polling connection to the Engine.IO server."""
+        if requests is None:  # pragma: no cover
+            # not installed
+            self.logger.error('requests package is not installed -- cannot '
+                              'send HTTP requests!')
+            return
+        self.base_url = self._get_engineio_url(url, engineio_path, 'polling')
+        self.logger.info('Attempting polling connection to ' + self.base_url)
+        r = self._send_request(
+            'GET', self.base_url + self._get_url_timestamp(), headers=headers,
+            timeout=self.request_timeout)
+        if r is None:
+            self._reset()
+            raise exceptions.ConnectionError(
+                'Connection refused by the server')
+        if r.status_code < 200 or r.status_code >= 300:
+            raise exceptions.ConnectionError(
+                'Unexpected status code {} in server response'.format(
+                    r.status_code))
+        try:
+            p = payload.Payload(encoded_payload=r.content)
+        except ValueError:
+            six.raise_from(exceptions.ConnectionError(
+                'Unexpected response from server'), None)
+        open_packet = p.packets[0]
+        if open_packet.packet_type != packet.OPEN:
+            raise exceptions.ConnectionError(
+                'OPEN packet not returned by server')
+        self.logger.info(
+            'Polling connection accepted with ' + str(open_packet.data))
+        self.sid = open_packet.data['sid']
+        self.upgrades = open_packet.data['upgrades']
+        self.ping_interval = open_packet.data['pingInterval'] / 1000.0
+        self.ping_timeout = open_packet.data['pingTimeout'] / 1000.0
+        self.current_transport = 'polling'
+        self.base_url += '&sid=' + self.sid
+
+        self.state = 'connected'
+        connected_clients.append(self)
+        self._trigger_event('connect', run_async=False)
+
+        for pkt in p.packets[1:]:
+            self._receive_packet(pkt)
+
+        if 'websocket' in self.upgrades and 'websocket' in self.transports:
+            # attempt to upgrade to websocket
+            if self._connect_websocket(url, headers, engineio_path):
+                # upgrade to websocket succeeded, we're done here
+                return
+
+        # start background tasks associated with this client
+        self.ping_loop_task = self.start_background_task(self._ping_loop)
+        self.write_loop_task = self.start_background_task(self._write_loop)
+        self.read_loop_task = self.start_background_task(
+            self._read_loop_polling)
+
+    def _connect_websocket(self, url, headers, engineio_path):
+        """Establish or upgrade to a WebSocket connection with the server."""
+        if websocket is None:  # pragma: no cover
+            # not installed
+            self.logger.warning('websocket-client package not installed, only '
+                                'polling transport is available')
+            return False
+        websocket_url = self._get_engineio_url(url, engineio_path, 'websocket')
+        if self.sid:
+            self.logger.info(
+                'Attempting WebSocket upgrade to ' + websocket_url)
+            upgrade = True
+            websocket_url += '&sid=' + self.sid
+        else:
+            upgrade = False
+            self.base_url = websocket_url
+            self.logger.info(
+                'Attempting WebSocket connection to ' + websocket_url)
+
+        # get the cookies from the long-polling connection so that they can
+        # also be sent the the WebSocket route
+        cookies = None
+        if self.http:
+            cookies = '; '.join(["{}={}".format(cookie.name, cookie.value)
+                                 for cookie in self.http.cookies])
+
+        try:
+            if not self.ssl_verify:
+                ws = websocket.create_connection(
+                    websocket_url + self._get_url_timestamp(), header=headers,
+                    cookie=cookies, sslopt={"cert_reqs": ssl.CERT_NONE})
+            else:
+                ws = websocket.create_connection(
+                    websocket_url + self._get_url_timestamp(), header=headers,
+                    cookie=cookies)
+        except (ConnectionError, IOError, websocket.WebSocketException):
+            if upgrade:
+                self.logger.warning(
+                    'WebSocket upgrade failed: connection error')
+                return False
+            else:
+                raise exceptions.ConnectionError('Connection error')
+        if upgrade:
+            p = packet.Packet(packet.PING,
+                              data=six.text_type('probe')).encode()
+            try:
+                ws.send(p)
+            except Exception as e:  # pragma: no cover
+                self.logger.warning(
+                    'WebSocket upgrade failed: unexpected send exception: %s',
+                    str(e))
+                return False
+            try:
+                p = ws.recv()
+            except Exception as e:  # pragma: no cover
+                self.logger.warning(
+                    'WebSocket upgrade failed: unexpected recv exception: %s',
+                    str(e))
+                return False
+            pkt = packet.Packet(encoded_packet=p)
+            if pkt.packet_type != packet.PONG or pkt.data != 'probe':
+                self.logger.warning(
+                    'WebSocket upgrade failed: no PONG packet')
+                return False
+            p = packet.Packet(packet.UPGRADE).encode()
+            try:
+                ws.send(p)
+            except Exception as e:  # pragma: no cover
+                self.logger.warning(
+                    'WebSocket upgrade failed: unexpected send exception: %s',
+                    str(e))
+                return False
+            self.current_transport = 'websocket'
+            self.logger.info('WebSocket upgrade was successful')
+        else:
+            try:
+                p = ws.recv()
+            except Exception as e:  # pragma: no cover
+                raise exceptions.ConnectionError(
+                    'Unexpected recv exception: ' + str(e))
+            open_packet = packet.Packet(encoded_packet=p)
+            if open_packet.packet_type != packet.OPEN:
+                raise exceptions.ConnectionError('no OPEN packet')
+            self.logger.info(
+                'WebSocket connection accepted with ' + str(open_packet.data))
+            self.sid = open_packet.data['sid']
+            self.upgrades = open_packet.data['upgrades']
+            self.ping_interval = open_packet.data['pingInterval'] / 1000.0
+            self.ping_timeout = open_packet.data['pingTimeout'] / 1000.0
+            self.current_transport = 'websocket'
+
+            self.state = 'connected'
+            connected_clients.append(self)
+            self._trigger_event('connect', run_async=False)
+        self.ws = ws
+
+        # start background tasks associated with this client
+        self.ping_loop_task = self.start_background_task(self._ping_loop)
+        self.write_loop_task = self.start_background_task(self._write_loop)
+        self.read_loop_task = self.start_background_task(
+            self._read_loop_websocket)
+        return True
+
+    def _receive_packet(self, pkt):
+        """Handle incoming packets from the server."""
+        packet_name = packet.packet_names[pkt.packet_type] \
+            if pkt.packet_type < len(packet.packet_names) else 'UNKNOWN'
+        self.logger.info(
+            'Received packet %s data %s', packet_name,
+            pkt.data if not isinstance(pkt.data, bytes) else '<binary>')
+        if pkt.packet_type == packet.MESSAGE:
+            self._trigger_event('message', pkt.data, run_async=True)
+        elif pkt.packet_type == packet.PONG:
+            self.pong_received = True
+        elif pkt.packet_type == packet.CLOSE:
+            self.disconnect(abort=True)
+        elif pkt.packet_type == packet.NOOP:
+            pass
+        else:
+            self.logger.error('Received unexpected packet of type %s',
+                              pkt.packet_type)
+
+    def _send_packet(self, pkt):
+        """Queue a packet to be sent to the server."""
+        if self.state != 'connected':
+            return
+        self.queue.put(pkt)
+        self.logger.info(
+            'Sending packet %s data %s',
+            packet.packet_names[pkt.packet_type],
+            pkt.data if not isinstance(pkt.data, bytes) else '<binary>')
+
+    def _send_request(
+            self, method, url, headers=None, body=None,
+            timeout=None):  # pragma: no cover
+        if self.http is None:
+            self.http = requests.Session()
+        try:
+            return self.http.request(method, url, headers=headers, data=body,
+                                     timeout=timeout, verify=self.ssl_verify)
+        except requests.exceptions.RequestException as exc:
+            self.logger.info('HTTP %s request to %s failed with error %s.',
+                             method, url, exc)
+
+    def _trigger_event(self, event, *args, **kwargs):
+        """Invoke an event handler."""
+        run_async = kwargs.pop('run_async', False)
+        if event in self.handlers:
+            if run_async:
+                return self.start_background_task(self.handlers[event], *args)
+            else:
+                try:
+                    return self.handlers[event](*args)
+                except:
+                    self.logger.exception(event + ' handler error')
+
+    def _get_engineio_url(self, url, engineio_path, transport):
+        """Generate the Engine.IO connection URL."""
+        engineio_path = engineio_path.strip('/')
+        parsed_url = urllib.parse.urlparse(url)
+
+        if transport == 'polling':
+            scheme = 'http'
+        elif transport == 'websocket':
+            scheme = 'ws'
+        else:  # pragma: no cover
+            raise ValueError('invalid transport')
+        if parsed_url.scheme in ['https', 'wss']:
+            scheme += 's'
+
+        return ('{scheme}://{netloc}/{path}/?{query}'
+                '{sep}transport={transport}&EIO=3').format(
+                    scheme=scheme, netloc=parsed_url.netloc,
+                    path=engineio_path, query=parsed_url.query,
+                    sep='&' if parsed_url.query else '',
+                    transport=transport)
+
+    def _get_url_timestamp(self):
+        """Generate the Engine.IO query string timestamp."""
+        return '&t=' + str(time.time())
+
+    def _ping_loop(self):
+        """This background task sends a PING to the server at the requested
+        interval.
+        """
+        self.pong_received = True
+        if self.ping_loop_event is None:
+            self.ping_loop_event = self.create_event()
+        else:
+            self.ping_loop_event.clear()
+        while self.state == 'connected':
+            if not self.pong_received:
+                self.logger.info(
+                    'PONG response has not been received, aborting')
+                if self.ws:
+                    self.ws.close(timeout=0)
+                self.queue.put(None)
+                break
+            self.pong_received = False
+            self._send_packet(packet.Packet(packet.PING))
+            self.ping_loop_event.wait(timeout=self.ping_interval)
+        self.logger.info('Exiting ping task')
+
+    def _read_loop_polling(self):
+        """Read packets by polling the Engine.IO server."""
+        while self.state == 'connected':
+            self.logger.info(
+                'Sending polling GET request to ' + self.base_url)
+            r = self._send_request(
+                'GET', self.base_url + self._get_url_timestamp(),
+                timeout=max(self.ping_interval, self.ping_timeout) + 5)
+            if r is None:
+                self.logger.warning(
+                    'Connection refused by the server, aborting')
+                self.queue.put(None)
+                break
+            if r.status_code < 200 or r.status_code >= 300:
+                self.logger.warning('Unexpected status code %s in server '
+                                    'response, aborting', r.status_code)
+                self.queue.put(None)
+                break
+            try:
+                p = payload.Payload(encoded_payload=r.content)
+            except ValueError:
+                self.logger.warning(
+                    'Unexpected packet from server, aborting')
+                self.queue.put(None)
+                break
+            for pkt in p.packets:
+                self._receive_packet(pkt)
+
+        self.logger.info('Waiting for write loop task to end')
+        self.write_loop_task.join()
+        self.logger.info('Waiting for ping loop task to end')
+        if self.ping_loop_event:  # pragma: no cover
+            self.ping_loop_event.set()
+        self.ping_loop_task.join()
+        if self.state == 'connected':
+            self._trigger_event('disconnect', run_async=False)
+            try:
+                connected_clients.remove(self)
+            except ValueError:  # pragma: no cover
+                pass
+            self._reset()
+        self.logger.info('Exiting read loop task')
+
+    def _read_loop_websocket(self):
+        """Read packets from the Engine.IO WebSocket connection."""
+        while self.state == 'connected':
+            p = None
+            try:
+                p = self.ws.recv()
+            except websocket.WebSocketConnectionClosedException:
+                self.logger.warning(
+                    'WebSocket connection was closed, aborting')
+                self.queue.put(None)
+                break
+            except Exception as e:
+                self.logger.info(
+                    'Unexpected error "%s", aborting', str(e))
+                self.queue.put(None)
+                break
+            if isinstance(p, six.text_type):  # pragma: no cover
+                p = p.encode('utf-8')
+            pkt = packet.Packet(encoded_packet=p)
+            self._receive_packet(pkt)
+
+        self.logger.info('Waiting for write loop task to end')
+        self.write_loop_task.join()
+        self.logger.info('Waiting for ping loop task to end')
+        if self.ping_loop_event:  # pragma: no cover
+            self.ping_loop_event.set()
+        self.ping_loop_task.join()
+        if self.state == 'connected':
+            self._trigger_event('disconnect', run_async=False)
+            try:
+                connected_clients.remove(self)
+            except ValueError:  # pragma: no cover
+                pass
+            self._reset()
+        self.logger.info('Exiting read loop task')
+
+    def _write_loop(self):
+        """This background task sends packages to the server as they are
+        pushed to the send queue.
+        """
+        while self.state == 'connected':
+            # to simplify the timeout handling, use the maximum of the
+            # ping interval and ping timeout as timeout, with an extra 5
+            # seconds grace period
+            timeout = max(self.ping_interval, self.ping_timeout) + 5
+            packets = None
+            try:
+                packets = [self.queue.get(timeout=timeout)]
+            except self.queue.Empty:
+                self.logger.error('packet queue is empty, aborting')
+                break
+            if packets == [None]:
+                self.queue.task_done()
+                packets = []
+            else:
+                while True:
+                    try:
+                        packets.append(self.queue.get(block=False))
+                    except self.queue.Empty:
+                        break
+                    if packets[-1] is None:
+                        packets = packets[:-1]
+                        self.queue.task_done()
+                        break
+            if not packets:
+                # empty packet list returned -> connection closed
+                break
+            if self.current_transport == 'polling':
+                p = payload.Payload(packets=packets)
+                r = self._send_request(
+                    'POST', self.base_url, body=p.encode(),
+                    headers={'Content-Type': 'application/octet-stream'},
+                    timeout=self.request_timeout)
+                for pkt in packets:
+                    self.queue.task_done()
+                if r is None:
+                    self.logger.warning(
+                        'Connection refused by the server, aborting')
+                    break
+                if r.status_code < 200 or r.status_code >= 300:
+                    self.logger.warning('Unexpected status code %s in server '
+                                        'response, aborting', r.status_code)
+                    self._reset()
+                    break
+            else:
+                # websocket
+                try:
+                    for pkt in packets:
+                        encoded_packet = pkt.encode(always_bytes=False)
+                        if pkt.binary:
+                            self.ws.send_binary(encoded_packet)
+                        else:
+                            self.ws.send(encoded_packet)
+                        self.queue.task_done()
+                except websocket.WebSocketConnectionClosedException:
+                    self.logger.warning(
+                        'WebSocket connection was closed, aborting')
+                    break
+        self.logger.info('Exiting write loop task')
diff --git a/libs/engineio/exceptions.py b/libs/engineio/exceptions.py
new file mode 100644
index 000000000..fb0b3e057
--- /dev/null
+++ b/libs/engineio/exceptions.py
@@ -0,0 +1,22 @@
+class EngineIOError(Exception):
+    pass
+
+
+class ContentTooLongError(EngineIOError):
+    pass
+
+
+class UnknownPacketError(EngineIOError):
+    pass
+
+
+class QueueEmpty(EngineIOError):
+    pass
+
+
+class SocketIsClosedError(EngineIOError):
+    pass
+
+
+class ConnectionError(EngineIOError):
+    pass
diff --git a/libs/engineio/middleware.py b/libs/engineio/middleware.py
new file mode 100644
index 000000000..d0bdcc747
--- /dev/null
+++ b/libs/engineio/middleware.py
@@ -0,0 +1,87 @@
+import os
+from engineio.static_files import get_static_file
+
+
+class WSGIApp(object):
+    """WSGI application middleware for Engine.IO.
+
+    This middleware dispatches traffic to an Engine.IO application. It can
+    also serve a list of static files to the client, or forward unrelated
+    HTTP traffic to another WSGI application.
+
+    :param engineio_app: The Engine.IO server. Must be an instance of the
+                         ``engineio.Server`` class.
+    :param wsgi_app: The WSGI app that receives all other traffic.
+    :param static_files: A dictionary with static file mapping rules. See the
+                         documentation for details on this argument.
+    :param engineio_path: The endpoint where the Engine.IO application should
+                          be installed. The default value is appropriate for
+                          most cases.
+
+    Example usage::
+
+        import engineio
+        import eventlet
+
+        eio = engineio.Server()
+        app = engineio.WSGIApp(eio, static_files={
+            '/': {'content_type': 'text/html', 'filename': 'index.html'},
+            '/index.html': {'content_type': 'text/html',
+                            'filename': 'index.html'},
+        })
+        eventlet.wsgi.server(eventlet.listen(('', 8000)), app)
+    """
+    def __init__(self, engineio_app, wsgi_app=None, static_files=None,
+                 engineio_path='engine.io'):
+        self.engineio_app = engineio_app
+        self.wsgi_app = wsgi_app
+        self.engineio_path = engineio_path.strip('/')
+        self.static_files = static_files or {}
+
+    def __call__(self, environ, start_response):
+        if 'gunicorn.socket' in environ:
+            # gunicorn saves the socket under environ['gunicorn.socket'], while
+            # eventlet saves it under environ['eventlet.input']. Eventlet also
+            # stores the socket inside a wrapper class, while gunicon writes it
+            # directly into the environment. To give eventlet's WebSocket
+            # module access to this socket when running under gunicorn, here we
+            # copy the socket to the eventlet format.
+            class Input(object):
+                def __init__(self, socket):
+                    self.socket = socket
+
+                def get_socket(self):
+                    return self.socket
+
+            environ['eventlet.input'] = Input(environ['gunicorn.socket'])
+        path = environ['PATH_INFO']
+        if path is not None and \
+                path.startswith('/{0}/'.format(self.engineio_path)):
+            return self.engineio_app.handle_request(environ, start_response)
+        else:
+            static_file = get_static_file(path, self.static_files) \
+                if self.static_files else None
+            if static_file:
+                if os.path.exists(static_file['filename']):
+                    start_response(
+                        '200 OK',
+                        [('Content-Type', static_file['content_type'])])
+                    with open(static_file['filename'], 'rb') as f:
+                        return [f.read()]
+                else:
+                    return self.not_found(start_response)
+            elif self.wsgi_app is not None:
+                return self.wsgi_app(environ, start_response)
+        return self.not_found(start_response)
+
+    def not_found(self, start_response):
+        start_response("404 Not Found", [('Content-Type', 'text/plain')])
+        return [b'Not Found']
+
+
+class Middleware(WSGIApp):
+    """This class has been renamed to ``WSGIApp`` and is now deprecated."""
+    def __init__(self, engineio_app, wsgi_app=None,
+                 engineio_path='engine.io'):
+        super(Middleware, self).__init__(engineio_app, wsgi_app,
+                                         engineio_path=engineio_path)
diff --git a/libs/engineio/packet.py b/libs/engineio/packet.py
new file mode 100644
index 000000000..a3aa6d476
--- /dev/null
+++ b/libs/engineio/packet.py
@@ -0,0 +1,92 @@
+import base64
+import json as _json
+
+import six
+
+(OPEN, CLOSE, PING, PONG, MESSAGE, UPGRADE, NOOP) = (0, 1, 2, 3, 4, 5, 6)
+packet_names = ['OPEN', 'CLOSE', 'PING', 'PONG', 'MESSAGE', 'UPGRADE', 'NOOP']
+
+binary_types = (six.binary_type, bytearray)
+
+
+class Packet(object):
+    """Engine.IO packet."""
+
+    json = _json
+
+    def __init__(self, packet_type=NOOP, data=None, binary=None,
+                 encoded_packet=None):
+        self.packet_type = packet_type
+        self.data = data
+        if binary is not None:
+            self.binary = binary
+        elif isinstance(data, six.text_type):
+            self.binary = False
+        elif isinstance(data, binary_types):
+            self.binary = True
+        else:
+            self.binary = False
+        if encoded_packet:
+            self.decode(encoded_packet)
+
+    def encode(self, b64=False, always_bytes=True):
+        """Encode the packet for transmission."""
+        if self.binary and not b64:
+            encoded_packet = six.int2byte(self.packet_type)
+        else:
+            encoded_packet = six.text_type(self.packet_type)
+            if self.binary and b64:
+                encoded_packet = 'b' + encoded_packet
+        if self.binary:
+            if b64:
+                encoded_packet += base64.b64encode(self.data).decode('utf-8')
+            else:
+                encoded_packet += self.data
+        elif isinstance(self.data, six.string_types):
+            encoded_packet += self.data
+        elif isinstance(self.data, dict) or isinstance(self.data, list):
+            encoded_packet += self.json.dumps(self.data,
+                                              separators=(',', ':'))
+        elif self.data is not None:
+            encoded_packet += str(self.data)
+        if always_bytes and not isinstance(encoded_packet, binary_types):
+            encoded_packet = encoded_packet.encode('utf-8')
+        return encoded_packet
+
+    def decode(self, encoded_packet):
+        """Decode a transmitted package."""
+        b64 = False
+        if not isinstance(encoded_packet, binary_types):
+            encoded_packet = encoded_packet.encode('utf-8')
+        elif not isinstance(encoded_packet, bytes):
+            encoded_packet = bytes(encoded_packet)
+        self.packet_type = six.byte2int(encoded_packet[0:1])
+        if self.packet_type == 98:  # 'b' --> binary base64 encoded packet
+            self.binary = True
+            encoded_packet = encoded_packet[1:]
+            self.packet_type = six.byte2int(encoded_packet[0:1])
+            self.packet_type -= 48
+            b64 = True
+        elif self.packet_type >= 48:
+            self.packet_type -= 48
+            self.binary = False
+        else:
+            self.binary = True
+        self.data = None
+        if len(encoded_packet) > 1:
+            if self.binary:
+                if b64:
+                    self.data = base64.b64decode(encoded_packet[1:])
+                else:
+                    self.data = encoded_packet[1:]
+            else:
+                try:
+                    self.data = self.json.loads(
+                        encoded_packet[1:].decode('utf-8'))
+                    if isinstance(self.data, int):
+                        # do not allow integer payloads, see
+                        # github.com/miguelgrinberg/python-engineio/issues/75
+                        # for background on this decision
+                        raise ValueError
+                except ValueError:
+                    self.data = encoded_packet[1:].decode('utf-8')
diff --git a/libs/engineio/payload.py b/libs/engineio/payload.py
new file mode 100644
index 000000000..fbf9cbd27
--- /dev/null
+++ b/libs/engineio/payload.py
@@ -0,0 +1,81 @@
+import six
+
+from . import packet
+
+from six.moves import urllib
+
+
+class Payload(object):
+    """Engine.IO payload."""
+    max_decode_packets = 16
+
+    def __init__(self, packets=None, encoded_payload=None):
+        self.packets = packets or []
+        if encoded_payload is not None:
+            self.decode(encoded_payload)
+
+    def encode(self, b64=False, jsonp_index=None):
+        """Encode the payload for transmission."""
+        encoded_payload = b''
+        for pkt in self.packets:
+            encoded_packet = pkt.encode(b64=b64)
+            packet_len = len(encoded_packet)
+            if b64:
+                encoded_payload += str(packet_len).encode('utf-8') + b':' + \
+                    encoded_packet
+            else:
+                binary_len = b''
+                while packet_len != 0:
+                    binary_len = six.int2byte(packet_len % 10) + binary_len
+                    packet_len = int(packet_len / 10)
+                if not pkt.binary:
+                    encoded_payload += b'\0'
+                else:
+                    encoded_payload += b'\1'
+                encoded_payload += binary_len + b'\xff' + encoded_packet
+        if jsonp_index is not None:
+            encoded_payload = b'___eio[' + \
+                              str(jsonp_index).encode() + \
+                              b']("' + \
+                              encoded_payload.replace(b'"', b'\\"') + \
+                              b'");'
+        return encoded_payload
+
+    def decode(self, encoded_payload):
+        """Decode a transmitted payload."""
+        self.packets = []
+
+        if len(encoded_payload) == 0:
+            return
+
+        # JSONP POST payload starts with 'd='
+        if encoded_payload.startswith(b'd='):
+            encoded_payload = urllib.parse.parse_qs(
+                encoded_payload)[b'd'][0]
+
+        i = 0
+        if six.byte2int(encoded_payload[0:1]) <= 1:
+            # binary encoding
+            while i < len(encoded_payload):
+                if len(self.packets) >= self.max_decode_packets:
+                    raise ValueError('Too many packets in payload')
+                packet_len = 0
+                i += 1
+                while six.byte2int(encoded_payload[i:i + 1]) != 255:
+                    packet_len = packet_len * 10 + six.byte2int(
+                        encoded_payload[i:i + 1])
+                    i += 1
+                self.packets.append(packet.Packet(
+                    encoded_packet=encoded_payload[i + 1:i + 1 + packet_len]))
+                i += packet_len + 1
+        else:
+            # assume text encoding
+            encoded_payload = encoded_payload.decode('utf-8')
+            while i < len(encoded_payload):
+                if len(self.packets) >= self.max_decode_packets:
+                    raise ValueError('Too many packets in payload')
+                j = encoded_payload.find(':', i)
+                packet_len = int(encoded_payload[i:j])
+                pkt = encoded_payload[j + 1:j + 1 + packet_len]
+                self.packets.append(packet.Packet(encoded_packet=pkt))
+                i = j + 1 + packet_len
diff --git a/libs/engineio/server.py b/libs/engineio/server.py
new file mode 100644
index 000000000..e1543c2dc
--- /dev/null
+++ b/libs/engineio/server.py
@@ -0,0 +1,675 @@
+import gzip
+import importlib
+import logging
+import uuid
+import zlib
+
+import six
+from six.moves import urllib
+
+from . import exceptions
+from . import packet
+from . import payload
+from . import socket
+
+default_logger = logging.getLogger('engineio.server')
+
+
+class Server(object):
+    """An Engine.IO server.
+
+    This class implements a fully compliant Engine.IO web server with support
+    for websocket and long-polling transports.
+
+    :param async_mode: The asynchronous model to use. See the Deployment
+                       section in the documentation for a description of the
+                       available options. Valid async modes are "threading",
+                       "eventlet", "gevent" and "gevent_uwsgi". If this
+                       argument is not given, "eventlet" is tried first, then
+                       "gevent_uwsgi", then "gevent", and finally "threading".
+                       The first async mode that has all its dependencies
+                       installed is the one that is chosen.
+    :param ping_timeout: The time in seconds that the client waits for the
+                         server to respond before disconnecting. The default
+                         is 60 seconds.
+    :param ping_interval: The interval in seconds at which the client pings
+                          the server. The default is 25 seconds. For advanced
+                          control, a two element tuple can be given, where
+                          the first number is the ping interval and the second
+                          is a grace period added by the server. The default
+                          grace period is 5 seconds.
+    :param max_http_buffer_size: The maximum size of a message when using the
+                                 polling transport. The default is 100,000,000
+                                 bytes.
+    :param allow_upgrades: Whether to allow transport upgrades or not. The
+                           default is ``True``.
+    :param http_compression: Whether to compress packages when using the
+                             polling transport. The default is ``True``.
+    :param compression_threshold: Only compress messages when their byte size
+                                  is greater than this value. The default is
+                                  1024 bytes.
+    :param cookie: Name of the HTTP cookie that contains the client session
+                   id. If set to ``None``, a cookie is not sent to the client.
+                   The default is ``'io'``.
+    :param cors_allowed_origins: Origin or list of origins that are allowed to
+                                 connect to this server. Only the same origin
+                                 is allowed by default. Set this argument to
+                                 ``'*'`` to allow all origins, or to ``[]`` to
+                                 disable CORS handling.
+    :param cors_credentials: Whether credentials (cookies, authentication) are
+                             allowed in requests to this server. The default
+                             is ``True``.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+    :param async_handlers: If set to ``True``, run message event handlers in
+                           non-blocking threads. To run handlers synchronously,
+                           set to ``False``. The default is ``True``.
+    :param monitor_clients: If set to ``True``, a background task will ensure
+                            inactive clients are closed. Set to ``False`` to
+                            disable the monitoring task (not recommended). The
+                            default is ``True``.
+    :param kwargs: Reserved for future extensions, any additional parameters
+                   given as keyword arguments will be silently ignored.
+    """
+    compression_methods = ['gzip', 'deflate']
+    event_names = ['connect', 'disconnect', 'message']
+    _default_monitor_clients = True
+
+    def __init__(self, async_mode=None, ping_timeout=60, ping_interval=25,
+                 max_http_buffer_size=100000000, allow_upgrades=True,
+                 http_compression=True, compression_threshold=1024,
+                 cookie='io', cors_allowed_origins=None,
+                 cors_credentials=True, logger=False, json=None,
+                 async_handlers=True, monitor_clients=None, **kwargs):
+        self.ping_timeout = ping_timeout
+        if isinstance(ping_interval, tuple):
+            self.ping_interval = ping_interval[0]
+            self.ping_interval_grace_period = ping_interval[1]
+        else:
+            self.ping_interval = ping_interval
+            self.ping_interval_grace_period = 5
+        self.max_http_buffer_size = max_http_buffer_size
+        self.allow_upgrades = allow_upgrades
+        self.http_compression = http_compression
+        self.compression_threshold = compression_threshold
+        self.cookie = cookie
+        self.cors_allowed_origins = cors_allowed_origins
+        self.cors_credentials = cors_credentials
+        self.async_handlers = async_handlers
+        self.sockets = {}
+        self.handlers = {}
+        self.start_service_task = monitor_clients \
+            if monitor_clients is not None else self._default_monitor_clients
+        if json is not None:
+            packet.Packet.json = json
+        if not isinstance(logger, bool):
+            self.logger = logger
+        else:
+            self.logger = default_logger
+            if not logging.root.handlers and \
+                    self.logger.level == logging.NOTSET:
+                if logger:
+                    self.logger.setLevel(logging.INFO)
+                else:
+                    self.logger.setLevel(logging.ERROR)
+                self.logger.addHandler(logging.StreamHandler())
+        modes = self.async_modes()
+        if async_mode is not None:
+            modes = [async_mode] if async_mode in modes else []
+        self._async = None
+        self.async_mode = None
+        for mode in modes:
+            try:
+                self._async = importlib.import_module(
+                    'engineio.async_drivers.' + mode)._async
+                asyncio_based = self._async['asyncio'] \
+                    if 'asyncio' in self._async else False
+                if asyncio_based != self.is_asyncio_based():
+                    continue  # pragma: no cover
+                self.async_mode = mode
+                break
+            except ImportError:
+                pass
+        if self.async_mode is None:
+            raise ValueError('Invalid async_mode specified')
+        if self.is_asyncio_based() and \
+                ('asyncio' not in self._async or not
+                 self._async['asyncio']):  # pragma: no cover
+            raise ValueError('The selected async_mode is not asyncio '
+                             'compatible')
+        if not self.is_asyncio_based() and 'asyncio' in self._async and \
+                self._async['asyncio']:  # pragma: no cover
+            raise ValueError('The selected async_mode requires asyncio and '
+                             'must use the AsyncServer class')
+        self.logger.info('Server initialized for %s.', self.async_mode)
+
+    def is_asyncio_based(self):
+        return False
+
+    def async_modes(self):
+        return ['eventlet', 'gevent_uwsgi', 'gevent', 'threading']
+
+    def on(self, event, handler=None):
+        """Register an event handler.
+
+        :param event: The event name. Can be ``'connect'``, ``'message'`` or
+                      ``'disconnect'``.
+        :param handler: The function that should be invoked to handle the
+                        event. When this parameter is not given, the method
+                        acts as a decorator for the handler function.
+
+        Example usage::
+
+            # as a decorator:
+            @eio.on('connect')
+            def connect_handler(sid, environ):
+                print('Connection request')
+                if environ['REMOTE_ADDR'] in blacklisted:
+                    return False  # reject
+
+            # as a method:
+            def message_handler(sid, msg):
+                print('Received message: ', msg)
+                eio.send(sid, 'response')
+            eio.on('message', message_handler)
+
+        The handler function receives the ``sid`` (session ID) for the
+        client as first argument. The ``'connect'`` event handler receives the
+        WSGI environment as a second argument, and can return ``False`` to
+        reject the connection. The ``'message'`` handler receives the message
+        payload as a second argument. The ``'disconnect'`` handler does not
+        take a second argument.
+        """
+        if event not in self.event_names:
+            raise ValueError('Invalid event')
+
+        def set_handler(handler):
+            self.handlers[event] = handler
+            return handler
+
+        if handler is None:
+            return set_handler
+        set_handler(handler)
+
+    def send(self, sid, data, binary=None):
+        """Send a message to a client.
+
+        :param sid: The session id of the recipient client.
+        :param data: The data to send to the client. Data can be of type
+                     ``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
+                     or ``dict``, the data will be serialized as JSON.
+        :param binary: ``True`` to send packet as binary, ``False`` to send
+                       as text. If not given, unicode (Python 2) and str
+                       (Python 3) are sent as text, and str (Python 2) and
+                       bytes (Python 3) are sent as binary.
+        """
+        try:
+            socket = self._get_socket(sid)
+        except KeyError:
+            # the socket is not available
+            self.logger.warning('Cannot send to sid %s', sid)
+            return
+        socket.send(packet.Packet(packet.MESSAGE, data=data, binary=binary))
+
+    def get_session(self, sid):
+        """Return the user session for a client.
+
+        :param sid: The session id of the client.
+
+        The return value is a dictionary. Modifications made to this
+        dictionary are not guaranteed to be preserved unless
+        ``save_session()`` is called, or when the ``session`` context manager
+        is used.
+        """
+        socket = self._get_socket(sid)
+        return socket.session
+
+    def save_session(self, sid, session):
+        """Store the user session for a client.
+
+        :param sid: The session id of the client.
+        :param session: The session dictionary.
+        """
+        socket = self._get_socket(sid)
+        socket.session = session
+
+    def session(self, sid):
+        """Return the user session for a client with context manager syntax.
+
+        :param sid: The session id of the client.
+
+        This is a context manager that returns the user session dictionary for
+        the client. Any changes that are made to this dictionary inside the
+        context manager block are saved back to the session. Example usage::
+
+            @eio.on('connect')
+            def on_connect(sid, environ):
+                username = authenticate_user(environ)
+                if not username:
+                    return False
+                with eio.session(sid) as session:
+                    session['username'] = username
+
+            @eio.on('message')
+            def on_message(sid, msg):
+                with eio.session(sid) as session:
+                    print('received message from ', session['username'])
+        """
+        class _session_context_manager(object):
+            def __init__(self, server, sid):
+                self.server = server
+                self.sid = sid
+                self.session = None
+
+            def __enter__(self):
+                self.session = self.server.get_session(sid)
+                return self.session
+
+            def __exit__(self, *args):
+                self.server.save_session(sid, self.session)
+
+        return _session_context_manager(self, sid)
+
+    def disconnect(self, sid=None):
+        """Disconnect a client.
+
+        :param sid: The session id of the client to close. If this parameter
+                    is not given, then all clients are closed.
+        """
+        if sid is not None:
+            try:
+                socket = self._get_socket(sid)
+            except KeyError:  # pragma: no cover
+                # the socket was already closed or gone
+                pass
+            else:
+                socket.close()
+                if sid in self.sockets:  # pragma: no cover
+                    del self.sockets[sid]
+        else:
+            for client in six.itervalues(self.sockets):
+                client.close()
+            self.sockets = {}
+
+    def transport(self, sid):
+        """Return the name of the transport used by the client.
+
+        The two possible values returned by this function are ``'polling'``
+        and ``'websocket'``.
+
+        :param sid: The session of the client.
+        """
+        return 'websocket' if self._get_socket(sid).upgraded else 'polling'
+
+    def handle_request(self, environ, start_response):
+        """Handle an HTTP request from the client.
+
+        This is the entry point of the Engine.IO application, using the same
+        interface as a WSGI application. For the typical usage, this function
+        is invoked by the :class:`Middleware` instance, but it can be invoked
+        directly when the middleware is not used.
+
+        :param environ: The WSGI environment.
+        :param start_response: The WSGI ``start_response`` function.
+
+        This function returns the HTTP response body to deliver to the client
+        as a byte sequence.
+        """
+        if self.cors_allowed_origins != []:
+            # Validate the origin header if present
+            # This is important for WebSocket more than for HTTP, since
+            # browsers only apply CORS controls to HTTP.
+            origin = environ.get('HTTP_ORIGIN')
+            if origin:
+                allowed_origins = self._cors_allowed_origins(environ)
+                if allowed_origins is not None and origin not in \
+                        allowed_origins:
+                    self.logger.info(origin + ' is not an accepted origin.')
+                    r = self._bad_request()
+                    start_response(r['status'], r['headers'])
+                    return [r['response']]
+
+        method = environ['REQUEST_METHOD']
+        query = urllib.parse.parse_qs(environ.get('QUERY_STRING', ''))
+
+        sid = query['sid'][0] if 'sid' in query else None
+        b64 = False
+        jsonp = False
+        jsonp_index = None
+
+        if 'b64' in query:
+            if query['b64'][0] == "1" or query['b64'][0].lower() == "true":
+                b64 = True
+        if 'j' in query:
+            jsonp = True
+            try:
+                jsonp_index = int(query['j'][0])
+            except (ValueError, KeyError, IndexError):
+                # Invalid JSONP index number
+                pass
+
+        if jsonp and jsonp_index is None:
+            self.logger.warning('Invalid JSONP index number')
+            r = self._bad_request()
+        elif method == 'GET':
+            if sid is None:
+                transport = query.get('transport', ['polling'])[0]
+                if transport != 'polling' and transport != 'websocket':
+                    self.logger.warning('Invalid transport %s', transport)
+                    r = self._bad_request()
+                else:
+                    r = self._handle_connect(environ, start_response,
+                                             transport, b64, jsonp_index)
+            else:
+                if sid not in self.sockets:
+                    self.logger.warning('Invalid session %s', sid)
+                    r = self._bad_request()
+                else:
+                    socket = self._get_socket(sid)
+                    try:
+                        packets = socket.handle_get_request(
+                            environ, start_response)
+                        if isinstance(packets, list):
+                            r = self._ok(packets, b64=b64,
+                                         jsonp_index=jsonp_index)
+                        else:
+                            r = packets
+                    except exceptions.EngineIOError:
+                        if sid in self.sockets:  # pragma: no cover
+                            self.disconnect(sid)
+                        r = self._bad_request()
+                    if sid in self.sockets and self.sockets[sid].closed:
+                        del self.sockets[sid]
+        elif method == 'POST':
+            if sid is None or sid not in self.sockets:
+                self.logger.warning('Invalid session %s', sid)
+                r = self._bad_request()
+            else:
+                socket = self._get_socket(sid)
+                try:
+                    socket.handle_post_request(environ)
+                    r = self._ok(jsonp_index=jsonp_index)
+                except exceptions.EngineIOError:
+                    if sid in self.sockets:  # pragma: no cover
+                        self.disconnect(sid)
+                    r = self._bad_request()
+                except:  # pragma: no cover
+                    # for any other unexpected errors, we log the error
+                    # and keep going
+                    self.logger.exception('post request handler error')
+                    r = self._ok(jsonp_index=jsonp_index)
+        elif method == 'OPTIONS':
+            r = self._ok()
+        else:
+            self.logger.warning('Method %s not supported', method)
+            r = self._method_not_found()
+
+        if not isinstance(r, dict):
+            return r or []
+        if self.http_compression and \
+                len(r['response']) >= self.compression_threshold:
+            encodings = [e.split(';')[0].strip() for e in
+                         environ.get('HTTP_ACCEPT_ENCODING', '').split(',')]
+            for encoding in encodings:
+                if encoding in self.compression_methods:
+                    r['response'] = \
+                        getattr(self, '_' + encoding)(r['response'])
+                    r['headers'] += [('Content-Encoding', encoding)]
+                    break
+        cors_headers = self._cors_headers(environ)
+        start_response(r['status'], r['headers'] + cors_headers)
+        return [r['response']]
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+        """
+        th = self._async['thread'](target=target, args=args, kwargs=kwargs)
+        th.start()
+        return th  # pragma: no cover
+
+    def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+        """
+        return self._async['sleep'](seconds)
+
+    def create_queue(self, *args, **kwargs):
+        """Create a queue object using the appropriate async model.
+
+        This is a utility function that applications can use to create a queue
+        without having to worry about using the correct call for the selected
+        async mode.
+        """
+        return self._async['queue'](*args, **kwargs)
+
+    def get_queue_empty_exception(self):
+        """Return the queue empty exception for the appropriate async model.
+
+        This is a utility function that applications can use to work with a
+        queue without having to worry about using the correct call for the
+        selected async mode.
+        """
+        return self._async['queue_empty']
+
+    def create_event(self, *args, **kwargs):
+        """Create an event object using the appropriate async model.
+
+        This is a utility function that applications can use to create an
+        event without having to worry about using the correct call for the
+        selected async mode.
+        """
+        return self._async['event'](*args, **kwargs)
+
+    def _generate_id(self):
+        """Generate a unique session id."""
+        return uuid.uuid4().hex
+
+    def _handle_connect(self, environ, start_response, transport, b64=False,
+                        jsonp_index=None):
+        """Handle a client connection request."""
+        if self.start_service_task:
+            # start the service task to monitor connected clients
+            self.start_service_task = False
+            self.start_background_task(self._service_task)
+
+        sid = self._generate_id()
+        s = socket.Socket(self, sid)
+        self.sockets[sid] = s
+
+        pkt = packet.Packet(
+            packet.OPEN, {'sid': sid,
+                          'upgrades': self._upgrades(sid, transport),
+                          'pingTimeout': int(self.ping_timeout * 1000),
+                          'pingInterval': int(self.ping_interval * 1000)})
+        s.send(pkt)
+
+        ret = self._trigger_event('connect', sid, environ, run_async=False)
+        if ret is False:
+            del self.sockets[sid]
+            self.logger.warning('Application rejected connection')
+            return self._unauthorized()
+
+        if transport == 'websocket':
+            ret = s.handle_get_request(environ, start_response)
+            if s.closed:
+                # websocket connection ended, so we are done
+                del self.sockets[sid]
+            return ret
+        else:
+            s.connected = True
+            headers = None
+            if self.cookie:
+                headers = [('Set-Cookie', self.cookie + '=' + sid)]
+            try:
+                return self._ok(s.poll(), headers=headers, b64=b64,
+                                jsonp_index=jsonp_index)
+            except exceptions.QueueEmpty:
+                return self._bad_request()
+
+    def _upgrades(self, sid, transport):
+        """Return the list of possible upgrades for a client connection."""
+        if not self.allow_upgrades or self._get_socket(sid).upgraded or \
+                self._async['websocket'] is None or transport == 'websocket':
+            return []
+        return ['websocket']
+
+    def _trigger_event(self, event, *args, **kwargs):
+        """Invoke an event handler."""
+        run_async = kwargs.pop('run_async', False)
+        if event in self.handlers:
+            if run_async:
+                return self.start_background_task(self.handlers[event], *args)
+            else:
+                try:
+                    return self.handlers[event](*args)
+                except:
+                    self.logger.exception(event + ' handler error')
+                    if event == 'connect':
+                        # if connect handler raised error we reject the
+                        # connection
+                        return False
+
+    def _get_socket(self, sid):
+        """Return the socket object for a given session."""
+        try:
+            s = self.sockets[sid]
+        except KeyError:
+            raise KeyError('Session not found')
+        if s.closed:
+            del self.sockets[sid]
+            raise KeyError('Session is disconnected')
+        return s
+
+    def _ok(self, packets=None, headers=None, b64=False, jsonp_index=None):
+        """Generate a successful HTTP response."""
+        if packets is not None:
+            if headers is None:
+                headers = []
+            if b64:
+                headers += [('Content-Type', 'text/plain; charset=UTF-8')]
+            else:
+                headers += [('Content-Type', 'application/octet-stream')]
+            return {'status': '200 OK',
+                    'headers': headers,
+                    'response': payload.Payload(packets=packets).encode(
+                        b64=b64, jsonp_index=jsonp_index)}
+        else:
+            return {'status': '200 OK',
+                    'headers': [('Content-Type', 'text/plain')],
+                    'response': b'OK'}
+
+    def _bad_request(self):
+        """Generate a bad request HTTP error response."""
+        return {'status': '400 BAD REQUEST',
+                'headers': [('Content-Type', 'text/plain')],
+                'response': b'Bad Request'}
+
+    def _method_not_found(self):
+        """Generate a method not found HTTP error response."""
+        return {'status': '405 METHOD NOT FOUND',
+                'headers': [('Content-Type', 'text/plain')],
+                'response': b'Method Not Found'}
+
+    def _unauthorized(self):
+        """Generate a unauthorized HTTP error response."""
+        return {'status': '401 UNAUTHORIZED',
+                'headers': [('Content-Type', 'text/plain')],
+                'response': b'Unauthorized'}
+
+    def _cors_allowed_origins(self, environ):
+        default_origins = []
+        if 'wsgi.url_scheme' in environ and 'HTTP_HOST' in environ:
+            default_origins.append('{scheme}://{host}'.format(
+                scheme=environ['wsgi.url_scheme'], host=environ['HTTP_HOST']))
+            if 'HTTP_X_FORWARDED_HOST' in environ:
+                scheme = environ.get(
+                    'HTTP_X_FORWARDED_PROTO',
+                    environ['wsgi.url_scheme']).split(',')[0].strip()
+                default_origins.append('{scheme}://{host}'.format(
+                    scheme=scheme, host=environ['HTTP_X_FORWARDED_HOST'].split(
+                        ',')[0].strip()))
+        if self.cors_allowed_origins is None:
+            allowed_origins = default_origins
+        elif self.cors_allowed_origins == '*':
+            allowed_origins = None
+        elif isinstance(self.cors_allowed_origins, six.string_types):
+            allowed_origins = [self.cors_allowed_origins]
+        else:
+            allowed_origins = self.cors_allowed_origins
+        return allowed_origins
+
+    def _cors_headers(self, environ):
+        """Return the cross-origin-resource-sharing headers."""
+        if self.cors_allowed_origins == []:
+            # special case, CORS handling is completely disabled
+            return []
+        headers = []
+        allowed_origins = self._cors_allowed_origins(environ)
+        if 'HTTP_ORIGIN' in environ and \
+                (allowed_origins is None or environ['HTTP_ORIGIN'] in
+                 allowed_origins):
+            headers = [('Access-Control-Allow-Origin', environ['HTTP_ORIGIN'])]
+        if environ['REQUEST_METHOD'] == 'OPTIONS':
+            headers += [('Access-Control-Allow-Methods', 'OPTIONS, GET, POST')]
+        if 'HTTP_ACCESS_CONTROL_REQUEST_HEADERS' in environ:
+            headers += [('Access-Control-Allow-Headers',
+                        environ['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])]
+        if self.cors_credentials:
+            headers += [('Access-Control-Allow-Credentials', 'true')]
+        return headers
+
+    def _gzip(self, response):
+        """Apply gzip compression to a response."""
+        bytesio = six.BytesIO()
+        with gzip.GzipFile(fileobj=bytesio, mode='w') as gz:
+            gz.write(response)
+        return bytesio.getvalue()
+
+    def _deflate(self, response):
+        """Apply deflate compression to a response."""
+        return zlib.compress(response)
+
+    def _service_task(self):  # pragma: no cover
+        """Monitor connected clients and clean up those that time out."""
+        while True:
+            if len(self.sockets) == 0:
+                # nothing to do
+                self.sleep(self.ping_timeout)
+                continue
+
+            # go through the entire client list in a ping interval cycle
+            sleep_interval = float(self.ping_timeout) / len(self.sockets)
+
+            try:
+                # iterate over the current clients
+                for s in self.sockets.copy().values():
+                    if not s.closing and not s.closed:
+                        s.check_ping_timeout()
+                    self.sleep(sleep_interval)
+            except (SystemExit, KeyboardInterrupt):
+                self.logger.info('service task canceled')
+                break
+            except:
+                # an unexpected exception has occurred, log it and continue
+                self.logger.exception('service task exception')
diff --git a/libs/engineio/socket.py b/libs/engineio/socket.py
new file mode 100644
index 000000000..38593e7c7
--- /dev/null
+++ b/libs/engineio/socket.py
@@ -0,0 +1,248 @@
+import six
+import sys
+import time
+
+from . import exceptions
+from . import packet
+from . import payload
+
+
+class Socket(object):
+    """An Engine.IO socket."""
+    upgrade_protocols = ['websocket']
+
+    def __init__(self, server, sid):
+        self.server = server
+        self.sid = sid
+        self.queue = self.server.create_queue()
+        self.last_ping = time.time()
+        self.connected = False
+        self.upgrading = False
+        self.upgraded = False
+        self.packet_backlog = []
+        self.closing = False
+        self.closed = False
+        self.session = {}
+
+    def poll(self):
+        """Wait for packets to send to the client."""
+        queue_empty = self.server.get_queue_empty_exception()
+        try:
+            packets = [self.queue.get(timeout=self.server.ping_timeout)]
+            self.queue.task_done()
+        except queue_empty:
+            raise exceptions.QueueEmpty()
+        if packets == [None]:
+            return []
+        while True:
+            try:
+                packets.append(self.queue.get(block=False))
+                self.queue.task_done()
+            except queue_empty:
+                break
+        return packets
+
+    def receive(self, pkt):
+        """Receive packet from the client."""
+        packet_name = packet.packet_names[pkt.packet_type] \
+            if pkt.packet_type < len(packet.packet_names) else 'UNKNOWN'
+        self.server.logger.info('%s: Received packet %s data %s',
+                                self.sid, packet_name,
+                                pkt.data if not isinstance(pkt.data, bytes)
+                                else '<binary>')
+        if pkt.packet_type == packet.PING:
+            self.last_ping = time.time()
+            self.send(packet.Packet(packet.PONG, pkt.data))
+        elif pkt.packet_type == packet.MESSAGE:
+            self.server._trigger_event('message', self.sid, pkt.data,
+                                       run_async=self.server.async_handlers)
+        elif pkt.packet_type == packet.UPGRADE:
+            self.send(packet.Packet(packet.NOOP))
+        elif pkt.packet_type == packet.CLOSE:
+            self.close(wait=False, abort=True)
+        else:
+            raise exceptions.UnknownPacketError()
+
+    def check_ping_timeout(self):
+        """Make sure the client is still sending pings.
+
+        This helps detect disconnections for long-polling clients.
+        """
+        if self.closed:
+            raise exceptions.SocketIsClosedError()
+        if time.time() - self.last_ping > self.server.ping_interval + \
+                self.server.ping_interval_grace_period:
+            self.server.logger.info('%s: Client is gone, closing socket',
+                                    self.sid)
+            # Passing abort=False here will cause close() to write a
+            # CLOSE packet. This has the effect of updating half-open sockets
+            # to their correct state of disconnected
+            self.close(wait=False, abort=False)
+            return False
+        return True
+
+    def send(self, pkt):
+        """Send a packet to the client."""
+        if not self.check_ping_timeout():
+            return
+        if self.upgrading:
+            self.packet_backlog.append(pkt)
+        else:
+            self.queue.put(pkt)
+        self.server.logger.info('%s: Sending packet %s data %s',
+                                self.sid, packet.packet_names[pkt.packet_type],
+                                pkt.data if not isinstance(pkt.data, bytes)
+                                else '<binary>')
+
+    def handle_get_request(self, environ, start_response):
+        """Handle a long-polling GET request from the client."""
+        connections = [
+            s.strip()
+            for s in environ.get('HTTP_CONNECTION', '').lower().split(',')]
+        transport = environ.get('HTTP_UPGRADE', '').lower()
+        if 'upgrade' in connections and transport in self.upgrade_protocols:
+            self.server.logger.info('%s: Received request to upgrade to %s',
+                                    self.sid, transport)
+            return getattr(self, '_upgrade_' + transport)(environ,
+                                                          start_response)
+        try:
+            packets = self.poll()
+        except exceptions.QueueEmpty:
+            exc = sys.exc_info()
+            self.close(wait=False)
+            six.reraise(*exc)
+        return packets
+
+    def handle_post_request(self, environ):
+        """Handle a long-polling POST request from the client."""
+        length = int(environ.get('CONTENT_LENGTH', '0'))
+        if length > self.server.max_http_buffer_size:
+            raise exceptions.ContentTooLongError()
+        else:
+            body = environ['wsgi.input'].read(length)
+            p = payload.Payload(encoded_payload=body)
+            for pkt in p.packets:
+                self.receive(pkt)
+
+    def close(self, wait=True, abort=False):
+        """Close the socket connection."""
+        if not self.closed and not self.closing:
+            self.closing = True
+            self.server._trigger_event('disconnect', self.sid, run_async=False)
+            if not abort:
+                self.send(packet.Packet(packet.CLOSE))
+            self.closed = True
+            self.queue.put(None)
+            if wait:
+                self.queue.join()
+
+    def _upgrade_websocket(self, environ, start_response):
+        """Upgrade the connection from polling to websocket."""
+        if self.upgraded:
+            raise IOError('Socket has been upgraded already')
+        if self.server._async['websocket'] is None:
+            # the selected async mode does not support websocket
+            return self.server._bad_request()
+        ws = self.server._async['websocket'](self._websocket_handler)
+        return ws(environ, start_response)
+
+    def _websocket_handler(self, ws):
+        """Engine.IO handler for websocket transport."""
+        # try to set a socket timeout matching the configured ping interval
+        for attr in ['_sock', 'socket']:  # pragma: no cover
+            if hasattr(ws, attr) and hasattr(getattr(ws, attr), 'settimeout'):
+                getattr(ws, attr).settimeout(self.server.ping_timeout)
+
+        if self.connected:
+            # the socket was already connected, so this is an upgrade
+            self.upgrading = True  # hold packet sends during the upgrade
+
+            pkt = ws.wait()
+            decoded_pkt = packet.Packet(encoded_packet=pkt)
+            if decoded_pkt.packet_type != packet.PING or \
+                    decoded_pkt.data != 'probe':
+                self.server.logger.info(
+                    '%s: Failed websocket upgrade, no PING packet', self.sid)
+                return []
+            ws.send(packet.Packet(
+                packet.PONG,
+                data=six.text_type('probe')).encode(always_bytes=False))
+            self.queue.put(packet.Packet(packet.NOOP))  # end poll
+
+            pkt = ws.wait()
+            decoded_pkt = packet.Packet(encoded_packet=pkt)
+            if decoded_pkt.packet_type != packet.UPGRADE:
+                self.upgraded = False
+                self.server.logger.info(
+                    ('%s: Failed websocket upgrade, expected UPGRADE packet, '
+                     'received %s instead.'),
+                    self.sid, pkt)
+                return []
+            self.upgraded = True
+
+            # flush any packets that were sent during the upgrade
+            for pkt in self.packet_backlog:
+                self.queue.put(pkt)
+            self.packet_backlog = []
+            self.upgrading = False
+        else:
+            self.connected = True
+            self.upgraded = True
+
+        # start separate writer thread
+        def writer():
+            while True:
+                packets = None
+                try:
+                    packets = self.poll()
+                except exceptions.QueueEmpty:
+                    break
+                if not packets:
+                    # empty packet list returned -> connection closed
+                    break
+                try:
+                    for pkt in packets:
+                        ws.send(pkt.encode(always_bytes=False))
+                except:
+                    break
+        writer_task = self.server.start_background_task(writer)
+
+        self.server.logger.info(
+            '%s: Upgrade to websocket successful', self.sid)
+
+        while True:
+            p = None
+            try:
+                p = ws.wait()
+            except Exception as e:
+                # if the socket is already closed, we can assume this is a
+                # downstream error of that
+                if not self.closed:  # pragma: no cover
+                    self.server.logger.info(
+                        '%s: Unexpected error "%s", closing connection',
+                        self.sid, str(e))
+                break
+            if p is None:
+                # connection closed by client
+                break
+            if isinstance(p, six.text_type):  # pragma: no cover
+                p = p.encode('utf-8')
+            pkt = packet.Packet(encoded_packet=p)
+            try:
+                self.receive(pkt)
+            except exceptions.UnknownPacketError:  # pragma: no cover
+                pass
+            except exceptions.SocketIsClosedError:  # pragma: no cover
+                self.server.logger.info('Receive error -- socket is closed')
+                break
+            except:  # pragma: no cover
+                # if we get an unexpected exception we log the error and exit
+                # the connection properly
+                self.server.logger.exception('Unknown receive error')
+                break
+
+        self.queue.put(None)  # unlock the writer task so that it can exit
+        writer_task.join()
+        self.close(wait=False, abort=True)
+
+        return []
diff --git a/libs/engineio/static_files.py b/libs/engineio/static_files.py
new file mode 100644
index 000000000..3058f6ea4
--- /dev/null
+++ b/libs/engineio/static_files.py
@@ -0,0 +1,55 @@
+content_types = {
+    'css': 'text/css',
+    'gif': 'image/gif',
+    'html': 'text/html',
+    'jpg': 'image/jpeg',
+    'js': 'application/javascript',
+    'json': 'application/json',
+    'png': 'image/png',
+    'txt': 'text/plain',
+}
+
+
+def get_static_file(path, static_files):
+    """Return the local filename and content type for the requested static
+    file URL.
+
+    :param path: the path portion of the requested URL.
+    :param static_files: a static file configuration dictionary.
+
+    This function returns a dictionary with two keys, "filename" and
+    "content_type". If the requested URL does not match any static file, the
+    return value is None.
+    """
+    if path in static_files:
+        f = static_files[path]
+    else:
+        f = None
+        rest = ''
+        while path != '':
+            path, last = path.rsplit('/', 1)
+            rest = '/' + last + rest
+            if path in static_files:
+                f = static_files[path] + rest
+                break
+            elif path + '/' in static_files:
+                f = static_files[path + '/'] + rest[1:]
+                break
+    if f:
+        if isinstance(f, str):
+            f = {'filename': f}
+        if f['filename'].endswith('/'):
+            if '' in static_files:
+                if isinstance(static_files[''], str):
+                    f['filename'] += static_files['']
+                else:
+                    f['filename'] += static_files['']['filename']
+                    if 'content_type' in static_files['']:
+                        f['content_type'] = static_files['']['content_type']
+            else:
+                f['filename'] += 'index.html'
+        if 'content_type' not in f:
+            ext = f['filename'].rsplit('.')[-1]
+            f['content_type'] = content_types.get(
+                ext, 'application/octet-stream')
+    return f
diff --git a/libs/flask_socketio/__init__.py b/libs/flask_socketio/__init__.py
new file mode 100644
index 000000000..e4209f1e9
--- /dev/null
+++ b/libs/flask_socketio/__init__.py
@@ -0,0 +1,922 @@
+from functools import wraps
+import os
+import sys
+
+# make sure gevent-socketio is not installed, as it conflicts with
+# python-socketio
+gevent_socketio_found = True
+try:
+    from socketio import socketio_manage
+except ImportError:
+    gevent_socketio_found = False
+if gevent_socketio_found:
+    print('The gevent-socketio package is incompatible with this version of '
+          'the Flask-SocketIO extension. Please uninstall it, and then '
+          'install the latest version of python-socketio in its place.')
+    sys.exit(1)
+
+import flask
+from flask import _request_ctx_stack, json as flask_json
+from flask.sessions import SessionMixin
+import socketio
+from socketio.exceptions import ConnectionRefusedError
+from werkzeug.debug import DebuggedApplication
+from werkzeug.serving import run_with_reloader
+
+from .namespace import Namespace
+from .test_client import SocketIOTestClient
+
+__version__ = '4.2.1'
+
+
+class _SocketIOMiddleware(socketio.WSGIApp):
+    """This WSGI middleware simply exposes the Flask application in the WSGI
+    environment before executing the request.
+    """
+    def __init__(self, socketio_app, flask_app, socketio_path='socket.io'):
+        self.flask_app = flask_app
+        super(_SocketIOMiddleware, self).__init__(socketio_app,
+                                                  flask_app.wsgi_app,
+                                                  socketio_path=socketio_path)
+
+    def __call__(self, environ, start_response):
+        environ = environ.copy()
+        environ['flask.app'] = self.flask_app
+        return super(_SocketIOMiddleware, self).__call__(environ,
+                                                         start_response)
+
+
+class _ManagedSession(dict, SessionMixin):
+    """This class is used for user sessions that are managed by
+    Flask-SocketIO. It is simple dict, expanded with the Flask session
+    attributes."""
+    pass
+
+
+class SocketIO(object):
+    """Create a Flask-SocketIO server.
+
+    :param app: The flask application instance. If the application instance
+                isn't known at the time this class is instantiated, then call
+                ``socketio.init_app(app)`` once the application instance is
+                available.
+    :param manage_session: If set to ``True``, this extension manages the user
+                           session for Socket.IO events. If set to ``False``,
+                           Flask's own session management is used. When using
+                           Flask's cookie based sessions it is recommended that
+                           you leave this set to the default of ``True``. When
+                           using server-side sessions, a ``False`` setting
+                           enables sharing the user session between HTTP routes
+                           and Socket.IO events.
+    :param message_queue: A connection URL for a message queue service the
+                          server can use for multi-process communication. A
+                          message queue is not required when using a single
+                          server process.
+    :param channel: The channel name, when using a message queue. If a channel
+                    isn't specified, a default channel will be used. If
+                    multiple clusters of SocketIO processes need to use the
+                    same message queue without interfering with each other, then
+                    each cluster should use a different channel.
+    :param path: The path where the Socket.IO server is exposed. Defaults to
+                 ``'socket.io'``. Leave this as is unless you know what you are
+                 doing.
+    :param resource: Alias to ``path``.
+    :param kwargs: Socket.IO and Engine.IO server options.
+
+    The Socket.IO server options are detailed below:
+
+    :param client_manager: The client manager instance that will manage the
+                           client list. When this is omitted, the client list
+                           is stored in an in-memory structure, so the use of
+                           multiple connected servers is not possible. In most
+                           cases, this argument does not need to be set
+                           explicitly.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param binary: ``True`` to support binary payloads, ``False`` to treat all
+                   payloads as text. On Python 2, if this is set to ``True``,
+                   ``unicode`` values are treated as text, and ``str`` and
+                   ``bytes`` values are treated as binary.  This option has no
+                   effect on Python 3, where text and binary payloads are
+                   always automatically discovered.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions. To use the same json encoder and decoder as a Flask
+                 application, use ``flask.json``.
+    :param async_handlers: If set to ``True``, event handlers for a client are
+                           executed in separate threads. To run handlers for a
+                           client synchronously, set to ``False``. The default
+                           is ``True``.
+    :param always_connect: When set to ``False``, new connections are
+                           provisory until the connect handler returns
+                           something other than ``False``, at which point they
+                           are accepted. When set to ``True``, connections are
+                           immediately accepted, and then if the connect
+                           handler returns ``False`` a disconnect is issued.
+                           Set to ``True`` if you need to emit events from the
+                           connect handler and your client is confused when it
+                           receives events before the connection acceptance.
+                           In any other case use the default of ``False``.
+
+    The Engine.IO server configuration supports the following settings:
+
+    :param async_mode: The asynchronous model to use. See the Deployment
+                       section in the documentation for a description of the
+                       available options. Valid async modes are
+                       ``threading``, ``eventlet``, ``gevent`` and
+                       ``gevent_uwsgi``. If this argument is not given,
+                       ``eventlet`` is tried first, then ``gevent_uwsgi``,
+                       then ``gevent``, and finally ``threading``. The
+                       first async mode that has all its dependencies installed
+                       is then one that is chosen.
+    :param ping_timeout: The time in seconds that the client waits for the
+                         server to respond before disconnecting. The default is
+                         60 seconds.
+    :param ping_interval: The interval in seconds at which the client pings
+                          the server. The default is 25 seconds.
+    :param max_http_buffer_size: The maximum size of a message when using the
+                                 polling transport. The default is 100,000,000
+                                 bytes.
+    :param allow_upgrades: Whether to allow transport upgrades or not. The
+                           default is ``True``.
+    :param http_compression: Whether to compress packages when using the
+                             polling transport. The default is ``True``.
+    :param compression_threshold: Only compress messages when their byte size
+                                  is greater than this value. The default is
+                                  1024 bytes.
+    :param cookie: Name of the HTTP cookie that contains the client session
+                   id. If set to ``None``, a cookie is not sent to the client.
+                   The default is ``'io'``.
+    :param cors_allowed_origins: Origin or list of origins that are allowed to
+                                 connect to this server. Only the same origin
+                                 is allowed by default. Set this argument to
+                                 ``'*'`` to allow all origins, or to ``[]`` to
+                                 disable CORS handling.
+    :param cors_credentials: Whether credentials (cookies, authentication) are
+                             allowed in requests to this server. The default is
+                             ``True``.
+    :param monitor_clients: If set to ``True``, a background task will ensure
+                            inactive clients are closed. Set to ``False`` to
+                            disable the monitoring task (not recommended). The
+                            default is ``True``.
+    :param engineio_logger: To enable Engine.IO logging set to ``True`` or pass
+                            a logger object to use. To disable logging set to
+                            ``False``. The default is ``False``.
+    """
+
+    def __init__(self, app=None, **kwargs):
+        self.server = None
+        self.server_options = {}
+        self.wsgi_server = None
+        self.handlers = []
+        self.namespace_handlers = []
+        self.exception_handlers = {}
+        self.default_exception_handler = None
+        self.manage_session = True
+        # We can call init_app when:
+        # - we were given the Flask app instance (standard initialization)
+        # - we were not given the app, but we were given a message_queue
+        #   (standard initialization for auxiliary process)
+        # In all other cases we collect the arguments and assume the client
+        # will call init_app from an app factory function.
+        if app is not None or 'message_queue' in kwargs:
+            self.init_app(app, **kwargs)
+        else:
+            self.server_options.update(kwargs)
+
+    def init_app(self, app, **kwargs):
+        if app is not None:
+            if not hasattr(app, 'extensions'):
+                app.extensions = {}  # pragma: no cover
+            app.extensions['socketio'] = self
+        self.server_options.update(kwargs)
+        self.manage_session = self.server_options.pop('manage_session',
+                                                      self.manage_session)
+
+        if 'client_manager' not in self.server_options:
+            url = self.server_options.pop('message_queue', None)
+            channel = self.server_options.pop('channel', 'flask-socketio')
+            write_only = app is None
+            if url:
+                if url.startswith(('redis://', "rediss://")):
+                    queue_class = socketio.RedisManager
+                elif url.startswith(('kafka://')):
+                    queue_class = socketio.KafkaManager
+                elif url.startswith('zmq'):
+                    queue_class = socketio.ZmqManager
+                else:
+                    queue_class = socketio.KombuManager
+                queue = queue_class(url, channel=channel,
+                                    write_only=write_only)
+                self.server_options['client_manager'] = queue
+
+        if 'json' in self.server_options and \
+                self.server_options['json'] == flask_json:
+            # flask's json module is tricky to use because its output
+            # changes when it is invoked inside or outside the app context
+            # so here to prevent any ambiguities we replace it with wrappers
+            # that ensure that the app context is always present
+            class FlaskSafeJSON(object):
+                @staticmethod
+                def dumps(*args, **kwargs):
+                    with app.app_context():
+                        return flask_json.dumps(*args, **kwargs)
+
+                @staticmethod
+                def loads(*args, **kwargs):
+                    with app.app_context():
+                        return flask_json.loads(*args, **kwargs)
+
+            self.server_options['json'] = FlaskSafeJSON
+
+        resource = self.server_options.pop('path', None) or \
+            self.server_options.pop('resource', None) or 'socket.io'
+        if resource.startswith('/'):
+            resource = resource[1:]
+        if os.environ.get('FLASK_RUN_FROM_CLI'):
+            if self.server_options.get('async_mode') is None:
+                if app is not None:
+                    app.logger.warning(
+                        'Flask-SocketIO is Running under Werkzeug, WebSocket '
+                        'is not available.')
+                self.server_options['async_mode'] = 'threading'
+        self.server = socketio.Server(**self.server_options)
+        self.async_mode = self.server.async_mode
+        for handler in self.handlers:
+            self.server.on(handler[0], handler[1], namespace=handler[2])
+        for namespace_handler in self.namespace_handlers:
+            self.server.register_namespace(namespace_handler)
+
+        if app is not None:
+            # here we attach the SocketIO middlware to the SocketIO object so it
+            # can be referenced later if debug middleware needs to be inserted
+            self.sockio_mw = _SocketIOMiddleware(self.server, app,
+                                                 socketio_path=resource)
+            app.wsgi_app = self.sockio_mw
+
+    def on(self, message, namespace=None):
+        """Decorator to register a SocketIO event handler.
+
+        This decorator must be applied to SocketIO event handlers. Example::
+
+            @socketio.on('my event', namespace='/chat')
+            def handle_my_custom_event(json):
+                print('received json: ' + str(json))
+
+        :param message: The name of the event. This is normally a user defined
+                        string, but a few event names are already defined. Use
+                        ``'message'`` to define a handler that takes a string
+                        payload, ``'json'`` to define a handler that takes a
+                        JSON blob payload, ``'connect'`` or ``'disconnect'``
+                        to create handlers for connection and disconnection
+                        events.
+        :param namespace: The namespace on which the handler is to be
+                          registered. Defaults to the global namespace.
+        """
+        namespace = namespace or '/'
+
+        def decorator(handler):
+            @wraps(handler)
+            def _handler(sid, *args):
+                return self._handle_event(handler, message, namespace, sid,
+                                          *args)
+
+            if self.server:
+                self.server.on(message, _handler, namespace=namespace)
+            else:
+                self.handlers.append((message, _handler, namespace))
+            return handler
+        return decorator
+
+    def on_error(self, namespace=None):
+        """Decorator to define a custom error handler for SocketIO events.
+
+        This decorator can be applied to a function that acts as an error
+        handler for a namespace. This handler will be invoked when a SocketIO
+        event handler raises an exception. The handler function must accept one
+        argument, which is the exception raised. Example::
+
+            @socketio.on_error(namespace='/chat')
+            def chat_error_handler(e):
+                print('An error has occurred: ' + str(e))
+
+        :param namespace: The namespace for which to register the error
+                          handler. Defaults to the global namespace.
+        """
+        namespace = namespace or '/'
+
+        def decorator(exception_handler):
+            if not callable(exception_handler):
+                raise ValueError('exception_handler must be callable')
+            self.exception_handlers[namespace] = exception_handler
+            return exception_handler
+        return decorator
+
+    def on_error_default(self, exception_handler):
+        """Decorator to define a default error handler for SocketIO events.
+
+        This decorator can be applied to a function that acts as a default
+        error handler for any namespaces that do not have a specific handler.
+        Example::
+
+            @socketio.on_error_default
+            def error_handler(e):
+                print('An error has occurred: ' + str(e))
+        """
+        if not callable(exception_handler):
+            raise ValueError('exception_handler must be callable')
+        self.default_exception_handler = exception_handler
+        return exception_handler
+
+    def on_event(self, message, handler, namespace=None):
+        """Register a SocketIO event handler.
+
+        ``on_event`` is the non-decorator version of ``'on'``.
+
+        Example::
+
+            def on_foo_event(json):
+                print('received json: ' + str(json))
+
+            socketio.on_event('my event', on_foo_event, namespace='/chat')
+
+        :param message: The name of the event. This is normally a user defined
+                        string, but a few event names are already defined. Use
+                        ``'message'`` to define a handler that takes a string
+                        payload, ``'json'`` to define a handler that takes a
+                        JSON blob payload, ``'connect'`` or ``'disconnect'``
+                        to create handlers for connection and disconnection
+                        events.
+        :param handler: The function that handles the event.
+        :param namespace: The namespace on which the handler is to be
+                          registered. Defaults to the global namespace.
+        """
+        self.on(message, namespace=namespace)(handler)
+
+    def on_namespace(self, namespace_handler):
+        if not isinstance(namespace_handler, Namespace):
+            raise ValueError('Not a namespace instance.')
+        namespace_handler._set_socketio(self)
+        if self.server:
+            self.server.register_namespace(namespace_handler)
+        else:
+            self.namespace_handlers.append(namespace_handler)
+
+    def emit(self, event, *args, **kwargs):
+        """Emit a server generated SocketIO event.
+
+        This function emits a SocketIO event to one or more connected clients.
+        A JSON blob can be attached to the event as payload. This function can
+        be used outside of a SocketIO event context, so it is appropriate to
+        use when the server is the originator of an event, outside of any
+        client context, such as in a regular HTTP request handler or a
+        background task. Example::
+
+            @app.route('/ping')
+            def ping():
+                socketio.emit('ping event', {'data': 42}, namespace='/chat')
+
+        :param event: The name of the user event to emit.
+        :param args: A dictionary with the JSON data to send as payload.
+        :param namespace: The namespace under which the message is to be sent.
+                          Defaults to the global namespace.
+        :param room: Send the message to all the users in the given room. If
+                     this parameter is not included, the event is sent to
+                     all connected users.
+        :param skip_sid: The session id of a client to ignore when broadcasting
+                         or addressing a room. This is typically set to the
+                         originator of the message, so that everyone except
+                         that client receive the message. To skip multiple sids
+                         pass a list.
+        :param callback: If given, this function will be called to acknowledge
+                         that the client has received the message. The
+                         arguments that will be passed to the function are
+                         those provided by the client. Callback functions can
+                         only be used when addressing an individual client.
+        """
+        namespace = kwargs.pop('namespace', '/')
+        room = kwargs.pop('room', None)
+        include_self = kwargs.pop('include_self', True)
+        skip_sid = kwargs.pop('skip_sid', None)
+        if not include_self and not skip_sid:
+            skip_sid = flask.request.sid
+        callback = kwargs.pop('callback', None)
+        if callback:
+            # wrap the callback so that it sets app app and request contexts
+            sid = flask.request.sid
+            original_callback = callback
+
+            def _callback_wrapper(*args):
+                return self._handle_event(original_callback, None, namespace,
+                                          sid, *args)
+
+            callback = _callback_wrapper
+        self.server.emit(event, *args, namespace=namespace, room=room,
+                         skip_sid=skip_sid, callback=callback, **kwargs)
+
+    def send(self, data, json=False, namespace=None, room=None,
+             callback=None, include_self=True, skip_sid=None, **kwargs):
+        """Send a server-generated SocketIO message.
+
+        This function sends a simple SocketIO message to one or more connected
+        clients. The message can be a string or a JSON blob. This is a simpler
+        version of ``emit()``, which should be preferred. This function can be
+        used outside of a SocketIO event context, so it is appropriate to use
+        when the server is the originator of an event.
+
+        :param data: The message to send, either a string or a JSON blob.
+        :param json: ``True`` if ``message`` is a JSON blob, ``False``
+                     otherwise.
+        :param namespace: The namespace under which the message is to be sent.
+                          Defaults to the global namespace.
+        :param room: Send the message only to the users in the given room. If
+                     this parameter is not included, the message is sent to
+                     all connected users.
+        :param skip_sid: The session id of a client to ignore when broadcasting
+                         or addressing a room. This is typically set to the
+                         originator of the message, so that everyone except
+                         that client receive the message. To skip multiple sids
+                         pass a list.
+        :param callback: If given, this function will be called to acknowledge
+                         that the client has received the message. The
+                         arguments that will be passed to the function are
+                         those provided by the client. Callback functions can
+                         only be used when addressing an individual client.
+        """
+        skip_sid = flask.request.sid if not include_self else skip_sid
+        if json:
+            self.emit('json', data, namespace=namespace, room=room,
+                      skip_sid=skip_sid, callback=callback, **kwargs)
+        else:
+            self.emit('message', data, namespace=namespace, room=room,
+                      skip_sid=skip_sid, callback=callback, **kwargs)
+
+    def close_room(self, room, namespace=None):
+        """Close a room.
+
+        This function removes any users that are in the given room and then
+        deletes the room from the server. This function can be used outside
+        of a SocketIO event context.
+
+        :param room: The name of the room to close.
+        :param namespace: The namespace under which the room exists. Defaults
+                          to the global namespace.
+        """
+        self.server.close_room(room, namespace)
+
+    def run(self, app, host=None, port=None, **kwargs):
+        """Run the SocketIO web server.
+
+        :param app: The Flask application instance.
+        :param host: The hostname or IP address for the server to listen on.
+                     Defaults to 127.0.0.1.
+        :param port: The port number for the server to listen on. Defaults to
+                     5000.
+        :param debug: ``True`` to start the server in debug mode, ``False`` to
+                      start in normal mode.
+        :param use_reloader: ``True`` to enable the Flask reloader, ``False``
+                             to disable it.
+        :param extra_files: A list of additional files that the Flask
+                            reloader should watch. Defaults to ``None``
+        :param log_output: If ``True``, the server logs all incomming
+                           connections. If ``False`` logging is disabled.
+                           Defaults to ``True`` in debug mode, ``False``
+                           in normal mode. Unused when the threading async
+                           mode is used.
+        :param kwargs: Additional web server options. The web server options
+                       are specific to the server used in each of the supported
+                       async modes. Note that options provided here will
+                       not be seen when using an external web server such
+                       as gunicorn, since this method is not called in that
+                       case.
+        """
+        if host is None:
+            host = '127.0.0.1'
+        if port is None:
+            server_name = app.config['SERVER_NAME']
+            if server_name and ':' in server_name:
+                port = int(server_name.rsplit(':', 1)[1])
+            else:
+                port = 5000
+
+        debug = kwargs.pop('debug', app.debug)
+        log_output = kwargs.pop('log_output', debug)
+        use_reloader = kwargs.pop('use_reloader', debug)
+        extra_files = kwargs.pop('extra_files', None)
+
+        app.debug = debug
+        if app.debug and self.server.eio.async_mode != 'threading':
+            # put the debug middleware between the SocketIO middleware
+            # and the Flask application instance
+            #
+            #    mw1   mw2   mw3   Flask app
+            #     o ---- o ---- o ---- o
+            #    /
+            #   o Flask-SocketIO
+            #    \  middleware
+            #     o
+            #  Flask-SocketIO WebSocket handler
+            #
+            # BECOMES
+            #
+            #  dbg-mw   mw1   mw2   mw3   Flask app
+            #     o ---- o ---- o ---- o ---- o
+            #    /
+            #   o Flask-SocketIO
+            #    \  middleware
+            #     o
+            #  Flask-SocketIO WebSocket handler
+            #
+            self.sockio_mw.wsgi_app = DebuggedApplication(self.sockio_mw.wsgi_app,
+                                                          evalex=True)
+
+        if self.server.eio.async_mode == 'threading':
+            from werkzeug._internal import _log
+            _log('warning', 'WebSocket transport not available. Install '
+                            'eventlet or gevent and gevent-websocket for '
+                            'improved performance.')
+            app.run(host=host, port=port, threaded=True,
+                    use_reloader=use_reloader, **kwargs)
+        elif self.server.eio.async_mode == 'eventlet':
+            def run_server():
+                import eventlet
+                import eventlet.wsgi
+                import eventlet.green
+                addresses = eventlet.green.socket.getaddrinfo(host, port)
+                if not addresses:
+                    raise RuntimeError('Could not resolve host to a valid address')
+                eventlet_socket = eventlet.listen(addresses[0][4], addresses[0][0])
+
+                # If provided an SSL argument, use an SSL socket
+                ssl_args = ['keyfile', 'certfile', 'server_side', 'cert_reqs',
+                            'ssl_version', 'ca_certs',
+                            'do_handshake_on_connect', 'suppress_ragged_eofs',
+                            'ciphers']
+                ssl_params = {k: kwargs[k] for k in kwargs if k in ssl_args}
+                if len(ssl_params) > 0:
+                    for k in ssl_params:
+                        kwargs.pop(k)
+                    ssl_params['server_side'] = True  # Listening requires true
+                    eventlet_socket = eventlet.wrap_ssl(eventlet_socket,
+                                                        **ssl_params)
+
+                eventlet.wsgi.server(eventlet_socket, app,
+                                     log_output=log_output, **kwargs)
+
+            if use_reloader:
+                run_with_reloader(run_server, extra_files=extra_files)
+            else:
+                run_server()
+        elif self.server.eio.async_mode == 'gevent':
+            from gevent import pywsgi
+            try:
+                from geventwebsocket.handler import WebSocketHandler
+                websocket = True
+            except ImportError:
+                websocket = False
+
+            log = 'default'
+            if not log_output:
+                log = None
+            if websocket:
+                self.wsgi_server = pywsgi.WSGIServer(
+                    (host, port), app, handler_class=WebSocketHandler,
+                    log=log, **kwargs)
+            else:
+                self.wsgi_server = pywsgi.WSGIServer((host, port), app,
+                                                     log=log, **kwargs)
+
+            if use_reloader:
+                # monkey patching is required by the reloader
+                from gevent import monkey
+                monkey.patch_thread()
+                monkey.patch_time()
+
+                def run_server():
+                    self.wsgi_server.serve_forever()
+
+                run_with_reloader(run_server, extra_files=extra_files)
+            else:
+                self.wsgi_server.serve_forever()
+
+    def stop(self):
+        """Stop a running SocketIO web server.
+
+        This method must be called from a HTTP or SocketIO handler function.
+        """
+        if self.server.eio.async_mode == 'threading':
+            func = flask.request.environ.get('werkzeug.server.shutdown')
+            if func:
+                func()
+            else:
+                raise RuntimeError('Cannot stop unknown web server')
+        elif self.server.eio.async_mode == 'eventlet':
+            raise SystemExit
+        elif self.server.eio.async_mode == 'gevent':
+            self.wsgi_server.stop()
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+        """
+        return self.server.start_background_task(target, *args, **kwargs)
+
+    def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+        """
+        return self.server.sleep(seconds)
+
+    def test_client(self, app, namespace=None, query_string=None,
+                    headers=None, flask_test_client=None):
+        """The Socket.IO test client is useful for testing a Flask-SocketIO
+        server. It works in a similar way to the Flask Test Client, but
+        adapted to the Socket.IO server.
+
+        :param app: The Flask application instance.
+        :param namespace: The namespace for the client. If not provided, the
+                          client connects to the server on the global
+                          namespace.
+        :param query_string: A string with custom query string arguments.
+        :param headers: A dictionary with custom HTTP headers.
+        :param flask_test_client: The instance of the Flask test client
+                                  currently in use. Passing the Flask test
+                                  client is optional, but is necessary if you
+                                  want the Flask user session and any other
+                                  cookies set in HTTP routes accessible from
+                                  Socket.IO events.
+        """
+        return SocketIOTestClient(app, self, namespace=namespace,
+                                  query_string=query_string, headers=headers,
+                                  flask_test_client=flask_test_client)
+
+    def _handle_event(self, handler, message, namespace, sid, *args):
+        if sid not in self.server.environ:
+            # we don't have record of this client, ignore this event
+            return '', 400
+        app = self.server.environ[sid]['flask.app']
+        with app.request_context(self.server.environ[sid]):
+            if self.manage_session:
+                # manage a separate session for this client's Socket.IO events
+                # created as a copy of the regular user session
+                if 'saved_session' not in self.server.environ[sid]:
+                    self.server.environ[sid]['saved_session'] = \
+                        _ManagedSession(flask.session)
+                session_obj = self.server.environ[sid]['saved_session']
+            else:
+                # let Flask handle the user session
+                # for cookie based sessions, this effectively freezes the
+                # session to its state at connection time
+                # for server-side sessions, this allows HTTP and Socket.IO to
+                # share the session, with both having read/write access to it
+                session_obj = flask.session._get_current_object()
+            _request_ctx_stack.top.session = session_obj
+            flask.request.sid = sid
+            flask.request.namespace = namespace
+            flask.request.event = {'message': message, 'args': args}
+            try:
+                if message == 'connect':
+                    ret = handler()
+                else:
+                    ret = handler(*args)
+            except:
+                err_handler = self.exception_handlers.get(
+                    namespace, self.default_exception_handler)
+                if err_handler is None:
+                    raise
+                type, value, traceback = sys.exc_info()
+                return err_handler(value)
+            if not self.manage_session:
+                # when Flask is managing the user session, it needs to save it
+                if not hasattr(session_obj, 'modified') or session_obj.modified:
+                    resp = app.response_class()
+                    app.session_interface.save_session(app, session_obj, resp)
+            return ret
+
+
+def emit(event, *args, **kwargs):
+    """Emit a SocketIO event.
+
+    This function emits a SocketIO event to one or more connected clients. A
+    JSON blob can be attached to the event as payload. This is a function that
+    can only be called from a SocketIO event handler, as in obtains some
+    information from the current client context. Example::
+
+        @socketio.on('my event')
+        def handle_my_custom_event(json):
+            emit('my response', {'data': 42})
+
+    :param event: The name of the user event to emit.
+    :param args: A dictionary with the JSON data to send as payload.
+    :param namespace: The namespace under which the message is to be sent.
+                      Defaults to the namespace used by the originating event.
+                      A ``'/'`` can be used to explicitly specify the global
+                      namespace.
+    :param callback: Callback function to invoke with the client's
+                     acknowledgement.
+    :param broadcast: ``True`` to send the message to all clients, or ``False``
+                      to only reply to the sender of the originating event.
+    :param room: Send the message to all the users in the given room. If this
+                 argument is set, then broadcast is implied to be ``True``.
+    :param include_self: ``True`` to include the sender when broadcasting or
+                         addressing a room, or ``False`` to send to everyone
+                         but the sender.
+    :param ignore_queue: Only used when a message queue is configured. If
+                         set to ``True``, the event is emitted to the
+                         clients directly, without going through the queue.
+                         This is more efficient, but only works when a
+                         single server process is used, or when there is a
+                         single addresee. It is recommended to always leave
+                         this parameter with its default value of ``False``.
+    """
+    if 'namespace' in kwargs:
+        namespace = kwargs['namespace']
+    else:
+        namespace = flask.request.namespace
+    callback = kwargs.get('callback')
+    broadcast = kwargs.get('broadcast')
+    room = kwargs.get('room')
+    if room is None and not broadcast:
+        room = flask.request.sid
+    include_self = kwargs.get('include_self', True)
+    ignore_queue = kwargs.get('ignore_queue', False)
+
+    socketio = flask.current_app.extensions['socketio']
+    return socketio.emit(event, *args, namespace=namespace, room=room,
+                         include_self=include_self, callback=callback,
+                         ignore_queue=ignore_queue)
+
+
+def send(message, **kwargs):
+    """Send a SocketIO message.
+
+    This function sends a simple SocketIO message to one or more connected
+    clients. The message can be a string or a JSON blob. This is a simpler
+    version of ``emit()``, which should be preferred. This is a function that
+    can only be called from a SocketIO event handler.
+
+    :param message: The message to send, either a string or a JSON blob.
+    :param json: ``True`` if ``message`` is a JSON blob, ``False``
+                     otherwise.
+    :param namespace: The namespace under which the message is to be sent.
+                      Defaults to the namespace used by the originating event.
+                      An empty string can be used to use the global namespace.
+    :param callback: Callback function to invoke with the client's
+                     acknowledgement.
+    :param broadcast: ``True`` to send the message to all connected clients, or
+                      ``False`` to only reply to the sender of the originating
+                      event.
+    :param room: Send the message to all the users in the given room.
+    :param include_self: ``True`` to include the sender when broadcasting or
+                         addressing a room, or ``False`` to send to everyone
+                         but the sender.
+    :param ignore_queue: Only used when a message queue is configured. If
+                         set to ``True``, the event is emitted to the
+                         clients directly, without going through the queue.
+                         This is more efficient, but only works when a
+                         single server process is used, or when there is a
+                         single addresee. It is recommended to always leave
+                         this parameter with its default value of ``False``.
+    """
+    json = kwargs.get('json', False)
+    if 'namespace' in kwargs:
+        namespace = kwargs['namespace']
+    else:
+        namespace = flask.request.namespace
+    callback = kwargs.get('callback')
+    broadcast = kwargs.get('broadcast')
+    room = kwargs.get('room')
+    if room is None and not broadcast:
+        room = flask.request.sid
+    include_self = kwargs.get('include_self', True)
+    ignore_queue = kwargs.get('ignore_queue', False)
+
+    socketio = flask.current_app.extensions['socketio']
+    return socketio.send(message, json=json, namespace=namespace, room=room,
+                         include_self=include_self, callback=callback,
+                         ignore_queue=ignore_queue)
+
+
+def join_room(room, sid=None, namespace=None):
+    """Join a room.
+
+    This function puts the user in a room, under the current namespace. The
+    user and the namespace are obtained from the event context. This is a
+    function that can only be called from a SocketIO event handler. Example::
+
+        @socketio.on('join')
+        def on_join(data):
+            username = session['username']
+            room = data['room']
+            join_room(room)
+            send(username + ' has entered the room.', room=room)
+
+    :param room: The name of the room to join.
+    :param sid: The session id of the client. If not provided, the client is
+                obtained from the request context.
+    :param namespace: The namespace for the room. If not provided, the
+                      namespace is obtained from the request context.
+    """
+    socketio = flask.current_app.extensions['socketio']
+    sid = sid or flask.request.sid
+    namespace = namespace or flask.request.namespace
+    socketio.server.enter_room(sid, room, namespace=namespace)
+
+
+def leave_room(room, sid=None, namespace=None):
+    """Leave a room.
+
+    This function removes the user from a room, under the current namespace.
+    The user and the namespace are obtained from the event context. Example::
+
+        @socketio.on('leave')
+        def on_leave(data):
+            username = session['username']
+            room = data['room']
+            leave_room(room)
+            send(username + ' has left the room.', room=room)
+
+    :param room: The name of the room to leave.
+    :param sid: The session id of the client. If not provided, the client is
+                obtained from the request context.
+    :param namespace: The namespace for the room. If not provided, the
+                      namespace is obtained from the request context.
+    """
+    socketio = flask.current_app.extensions['socketio']
+    sid = sid or flask.request.sid
+    namespace = namespace or flask.request.namespace
+    socketio.server.leave_room(sid, room, namespace=namespace)
+
+
+def close_room(room, namespace=None):
+    """Close a room.
+
+    This function removes any users that are in the given room and then deletes
+    the room from the server.
+
+    :param room: The name of the room to close.
+    :param namespace: The namespace for the room. If not provided, the
+                      namespace is obtained from the request context.
+    """
+    socketio = flask.current_app.extensions['socketio']
+    namespace = namespace or flask.request.namespace
+    socketio.server.close_room(room, namespace=namespace)
+
+
+def rooms(sid=None, namespace=None):
+    """Return a list of the rooms the client is in.
+
+    This function returns all the rooms the client has entered, including its
+    own room, assigned by the Socket.IO server.
+
+    :param sid: The session id of the client. If not provided, the client is
+                obtained from the request context.
+    :param namespace: The namespace for the room. If not provided, the
+                      namespace is obtained from the request context.
+    """
+    socketio = flask.current_app.extensions['socketio']
+    sid = sid or flask.request.sid
+    namespace = namespace or flask.request.namespace
+    return socketio.server.rooms(sid, namespace=namespace)
+
+
+def disconnect(sid=None, namespace=None, silent=False):
+    """Disconnect the client.
+
+    This function terminates the connection with the client. As a result of
+    this call the client will receive a disconnect event. Example::
+
+        @socketio.on('message')
+        def receive_message(msg):
+            if is_banned(session['username']):
+                disconnect()
+            else:
+                # ...
+
+    :param sid: The session id of the client. If not provided, the client is
+                obtained from the request context.
+    :param namespace: The namespace for the room. If not provided, the
+                      namespace is obtained from the request context.
+    :param silent: this option is deprecated.
+    """
+    socketio = flask.current_app.extensions['socketio']
+    sid = sid or flask.request.sid
+    namespace = namespace or flask.request.namespace
+    return socketio.server.disconnect(sid, namespace=namespace)
diff --git a/libs/flask_socketio/namespace.py b/libs/flask_socketio/namespace.py
new file mode 100644
index 000000000..914ff3816
--- /dev/null
+++ b/libs/flask_socketio/namespace.py
@@ -0,0 +1,47 @@
+from socketio import Namespace as _Namespace
+
+
+class Namespace(_Namespace):
+    def __init__(self, namespace=None):
+        super(Namespace, self).__init__(namespace)
+        self.socketio = None
+
+    def _set_socketio(self, socketio):
+        self.socketio = socketio
+
+    def trigger_event(self, event, *args):
+        """Dispatch an event to the proper handler method.
+
+        In the most common usage, this method is not overloaded by subclasses,
+        as it performs the routing of events to methods. However, this
+        method can be overriden if special dispatching rules are needed, or if
+        having a single method that catches all events is desired.
+        """
+        handler_name = 'on_' + event
+        if not hasattr(self, handler_name):
+            # there is no handler for this event, so we ignore it
+            return
+        handler = getattr(self, handler_name)
+        return self.socketio._handle_event(handler, event, self.namespace,
+                                           *args)
+
+    def emit(self, event, data=None, room=None, include_self=True,
+             namespace=None, callback=None):
+        """Emit a custom event to one or more connected clients."""
+        return self.socketio.emit(event, data, room=room,
+                                  include_self=include_self,
+                                  namespace=namespace or self.namespace,
+                                  callback=callback)
+
+    def send(self, data, room=None, include_self=True, namespace=None,
+             callback=None):
+        """Send a message to one or more connected clients."""
+        return self.socketio.send(data, room=room, include_self=include_self,
+                                  namespace=namespace or self.namespace,
+                                  callback=callback)
+
+    def close_room(self, room, namespace=None):
+        """Close a room."""
+        return self.socketio.close_room(room=room,
+                                        namespace=namespace or self.namespace)
+
diff --git a/libs/flask_socketio/test_client.py b/libs/flask_socketio/test_client.py
new file mode 100644
index 000000000..0c4592034
--- /dev/null
+++ b/libs/flask_socketio/test_client.py
@@ -0,0 +1,205 @@
+import uuid
+
+from socketio import packet
+from socketio.pubsub_manager import PubSubManager
+from werkzeug.test import EnvironBuilder
+
+
+class SocketIOTestClient(object):
+    """
+    This class is useful for testing a Flask-SocketIO server. It works in a
+    similar way to the Flask Test Client, but adapted to the Socket.IO server.
+
+    :param app: The Flask application instance.
+    :param socketio: The application's ``SocketIO`` instance.
+    :param namespace: The namespace for the client. If not provided, the client
+                      connects to the server on the global namespace.
+    :param query_string: A string with custom query string arguments.
+    :param headers: A dictionary with custom HTTP headers.
+    :param flask_test_client: The instance of the Flask test client
+                              currently in use. Passing the Flask test
+                              client is optional, but is necessary if you
+                              want the Flask user session and any other
+                              cookies set in HTTP routes accessible from
+                              Socket.IO events.
+    """
+    queue = {}
+    acks = {}
+
+    def __init__(self, app, socketio, namespace=None, query_string=None,
+                 headers=None, flask_test_client=None):
+        def _mock_send_packet(sid, pkt):
+            if pkt.packet_type == packet.EVENT or \
+                    pkt.packet_type == packet.BINARY_EVENT:
+                if sid not in self.queue:
+                    self.queue[sid] = []
+                if pkt.data[0] == 'message' or pkt.data[0] == 'json':
+                    self.queue[sid].append({'name': pkt.data[0],
+                                            'args': pkt.data[1],
+                                            'namespace': pkt.namespace or '/'})
+                else:
+                    self.queue[sid].append({'name': pkt.data[0],
+                                            'args': pkt.data[1:],
+                                            'namespace': pkt.namespace or '/'})
+            elif pkt.packet_type == packet.ACK or \
+                    pkt.packet_type == packet.BINARY_ACK:
+                self.acks[sid] = {'args': pkt.data,
+                                  'namespace': pkt.namespace or '/'}
+            elif pkt.packet_type == packet.DISCONNECT:
+                self.connected[pkt.namespace or '/'] = False
+
+        self.app = app
+        self.flask_test_client = flask_test_client
+        self.sid = uuid.uuid4().hex
+        self.queue[self.sid] = []
+        self.acks[self.sid] = None
+        self.callback_counter = 0
+        self.socketio = socketio
+        self.connected = {}
+        socketio.server._send_packet = _mock_send_packet
+        socketio.server.environ[self.sid] = {}
+        socketio.server.async_handlers = False      # easier to test when
+        socketio.server.eio.async_handlers = False  # events are sync
+        if isinstance(socketio.server.manager, PubSubManager):
+            raise RuntimeError('Test client cannot be used with a message '
+                               'queue. Disable the queue on your test '
+                               'configuration.')
+        socketio.server.manager.initialize()
+        self.connect(namespace=namespace, query_string=query_string,
+                     headers=headers)
+
+    def is_connected(self, namespace=None):
+        """Check if a namespace is connected.
+
+        :param namespace: The namespace to check. The global namespace is
+                         assumed if this argument is not provided.
+        """
+        return self.connected.get(namespace or '/', False)
+
+    def connect(self, namespace=None, query_string=None, headers=None):
+        """Connect the client.
+
+        :param namespace: The namespace for the client. If not provided, the
+                          client connects to the server on the global
+                          namespace.
+        :param query_string: A string with custom query string arguments.
+        :param headers: A dictionary with custom HTTP headers.
+
+        Note that it is usually not necessary to explicitly call this method,
+        since a connection is automatically established when an instance of
+        this class is created. An example where it this method would be useful
+        is when the application accepts multiple namespace connections.
+        """
+        url = '/socket.io'
+        if query_string:
+            if query_string[0] != '?':
+                query_string = '?' + query_string
+            url += query_string
+        environ = EnvironBuilder(url, headers=headers).get_environ()
+        environ['flask.app'] = self.app
+        if self.flask_test_client:
+            # inject cookies from Flask
+            self.flask_test_client.cookie_jar.inject_wsgi(environ)
+        self.connected['/'] = True
+        if self.socketio.server._handle_eio_connect(
+                self.sid, environ) is False:
+            del self.connected['/']
+        if namespace is not None and namespace != '/':
+            self.connected[namespace] = True
+            pkt = packet.Packet(packet.CONNECT, namespace=namespace)
+            with self.app.app_context():
+                if self.socketio.server._handle_eio_message(
+                        self.sid, pkt.encode()) is False:
+                    del self.connected[namespace]
+
+    def disconnect(self, namespace=None):
+        """Disconnect the client.
+
+        :param namespace: The namespace to disconnect. The global namespace is
+                         assumed if this argument is not provided.
+        """
+        if not self.is_connected(namespace):
+            raise RuntimeError('not connected')
+        pkt = packet.Packet(packet.DISCONNECT, namespace=namespace)
+        with self.app.app_context():
+            self.socketio.server._handle_eio_message(self.sid, pkt.encode())
+        del self.connected[namespace or '/']
+
+    def emit(self, event, *args, **kwargs):
+        """Emit an event to the server.
+
+        :param event: The event name.
+        :param *args: The event arguments.
+        :param callback: ``True`` if the client requests a callback, ``False``
+                         if not. Note that client-side callbacks are not
+                         implemented, a callback request will just tell the
+                         server to provide the arguments to invoke the
+                         callback, but no callback is invoked. Instead, the
+                         arguments that the server provided for the callback
+                         are returned by this function.
+        :param namespace: The namespace of the event. The global namespace is
+                          assumed if this argument is not provided.
+        """
+        namespace = kwargs.pop('namespace', None)
+        if not self.is_connected(namespace):
+            raise RuntimeError('not connected')
+        callback = kwargs.pop('callback', False)
+        id = None
+        if callback:
+            self.callback_counter += 1
+            id = self.callback_counter
+        pkt = packet.Packet(packet.EVENT, data=[event] + list(args),
+                            namespace=namespace, id=id)
+        with self.app.app_context():
+            encoded_pkt = pkt.encode()
+            if isinstance(encoded_pkt, list):
+                for epkt in encoded_pkt:
+                    self.socketio.server._handle_eio_message(self.sid, epkt)
+            else:
+                self.socketio.server._handle_eio_message(self.sid, encoded_pkt)
+        ack = self.acks.pop(self.sid, None)
+        if ack is not None:
+            return ack['args'][0] if len(ack['args']) == 1 \
+                else ack['args']
+
+    def send(self, data, json=False, callback=False, namespace=None):
+        """Send a text or JSON message to the server.
+
+        :param data: A string, dictionary or list to send to the server.
+        :param json: ``True`` to send a JSON message, ``False`` to send a text
+                     message.
+        :param callback: ``True`` if the client requests a callback, ``False``
+                         if not. Note that client-side callbacks are not
+                         implemented, a callback request will just tell the
+                         server to provide the arguments to invoke the
+                         callback, but no callback is invoked. Instead, the
+                         arguments that the server provided for the callback
+                         are returned by this function.
+        :param namespace: The namespace of the event. The global namespace is
+                          assumed if this argument is not provided.
+        """
+        if json:
+            msg = 'json'
+        else:
+            msg = 'message'
+        return self.emit(msg, data, callback=callback, namespace=namespace)
+
+    def get_received(self, namespace=None):
+        """Return the list of messages received from the server.
+
+        Since this is not a real client, any time the server emits an event,
+        the event is simply stored. The test code can invoke this method to
+        obtain the list of events that were received since the last call.
+
+        :param namespace: The namespace to get events from. The global
+                          namespace is assumed if this argument is not
+                          provided.
+        """
+        if not self.is_connected(namespace):
+            raise RuntimeError('not connected')
+        namespace = namespace or '/'
+        r = [pkt for pkt in self.queue[self.sid]
+             if pkt['namespace'] == namespace]
+        self.queue[self.sid] = [pkt for pkt in self.queue[self.sid]
+                                if pkt not in r]
+        return r
diff --git a/libs/socketio/__init__.py b/libs/socketio/__init__.py
new file mode 100644
index 000000000..d3ee7242b
--- /dev/null
+++ b/libs/socketio/__init__.py
@@ -0,0 +1,38 @@
+import sys
+
+from .client import Client
+from .base_manager import BaseManager
+from .pubsub_manager import PubSubManager
+from .kombu_manager import KombuManager
+from .redis_manager import RedisManager
+from .kafka_manager import KafkaManager
+from .zmq_manager import ZmqManager
+from .server import Server
+from .namespace import Namespace, ClientNamespace
+from .middleware import WSGIApp, Middleware
+from .tornado import get_tornado_handler
+if sys.version_info >= (3, 5):  # pragma: no cover
+    from .asyncio_client import AsyncClient
+    from .asyncio_server import AsyncServer
+    from .asyncio_manager import AsyncManager
+    from .asyncio_namespace import AsyncNamespace, AsyncClientNamespace
+    from .asyncio_redis_manager import AsyncRedisManager
+    from .asyncio_aiopika_manager import AsyncAioPikaManager
+    from .asgi import ASGIApp
+else:  # pragma: no cover
+    AsyncClient = None
+    AsyncServer = None
+    AsyncManager = None
+    AsyncNamespace = None
+    AsyncRedisManager = None
+    AsyncAioPikaManager = None
+
+__version__ = '4.4.0'
+
+__all__ = ['__version__', 'Client', 'Server', 'BaseManager', 'PubSubManager',
+           'KombuManager', 'RedisManager', 'ZmqManager', 'KafkaManager',
+           'Namespace', 'ClientNamespace', 'WSGIApp', 'Middleware']
+if AsyncServer is not None:  # pragma: no cover
+    __all__ += ['AsyncClient', 'AsyncServer', 'AsyncNamespace',
+                'AsyncClientNamespace', 'AsyncManager', 'AsyncRedisManager',
+                'ASGIApp', 'get_tornado_handler', 'AsyncAioPikaManager']
diff --git a/libs/socketio/asgi.py b/libs/socketio/asgi.py
new file mode 100644
index 000000000..9bcdd03ba
--- /dev/null
+++ b/libs/socketio/asgi.py
@@ -0,0 +1,36 @@
+import engineio
+
+
+class ASGIApp(engineio.ASGIApp):  # pragma: no cover
+    """ASGI application middleware for Socket.IO.
+
+    This middleware dispatches traffic to an Socket.IO application. It can
+    also serve a list of static files to the client, or forward unrelated
+    HTTP traffic to another ASGI application.
+
+    :param socketio_server: The Socket.IO server. Must be an instance of the
+                            ``socketio.AsyncServer`` class.
+    :param static_files: A dictionary with static file mapping rules. See the
+                         documentation for details on this argument.
+    :param other_asgi_app: A separate ASGI app that receives all other traffic.
+    :param socketio_path: The endpoint where the Socket.IO application should
+                          be installed. The default value is appropriate for
+                          most cases.
+
+    Example usage::
+
+        import socketio
+        import uvicorn
+
+        sio = socketio.AsyncServer()
+        app = engineio.ASGIApp(sio, static_files={
+            '/': 'index.html',
+            '/static': './public',
+        })
+        uvicorn.run(app, host='127.0.0.1', port=5000)
+    """
+    def __init__(self, socketio_server, other_asgi_app=None,
+                 static_files=None, socketio_path='socket.io'):
+        super().__init__(socketio_server, other_asgi_app,
+                         static_files=static_files,
+                         engineio_path=socketio_path)
diff --git a/libs/socketio/asyncio_aiopika_manager.py b/libs/socketio/asyncio_aiopika_manager.py
new file mode 100644
index 000000000..b20d6afd9
--- /dev/null
+++ b/libs/socketio/asyncio_aiopika_manager.py
@@ -0,0 +1,105 @@
+import asyncio
+import pickle
+
+from socketio.asyncio_pubsub_manager import AsyncPubSubManager
+
+try:
+    import aio_pika
+except ImportError:
+    aio_pika = None
+
+
+class AsyncAioPikaManager(AsyncPubSubManager):  # pragma: no cover
+    """Client manager that uses aio_pika for inter-process messaging under
+    asyncio.
+
+    This class implements a client manager backend for event sharing across
+    multiple processes, using RabbitMQ
+
+    To use a aio_pika backend, initialize the :class:`Server` instance as
+    follows::
+
+        url = 'amqp://user:password@hostname:port//'
+        server = socketio.Server(client_manager=socketio.AsyncAioPikaManager(
+            url))
+
+    :param url: The connection URL for the backend messaging queue. Example
+                connection URLs are ``'amqp://guest:guest@localhost:5672//'``
+                for RabbitMQ.
+    :param channel: The channel name on which the server sends and receives
+                    notifications. Must be the same in all the servers.
+                    With this manager, the channel name is the exchange name
+                    in rabbitmq
+    :param write_only: If set ot ``True``, only initialize to emit events. The
+                       default of ``False`` initializes the class for emitting
+                       and receiving.
+    """
+
+    name = 'asyncaiopika'
+
+    def __init__(self, url='amqp://guest:guest@localhost:5672//',
+                 channel='socketio', write_only=False, logger=None):
+        if aio_pika is None:
+            raise RuntimeError('aio_pika package is not installed '
+                               '(Run "pip install aio_pika" in your '
+                               'virtualenv).')
+        self.url = url
+        self.listener_connection = None
+        self.listener_channel = None
+        self.listener_queue = None
+        super().__init__(channel=channel, write_only=write_only, logger=logger)
+
+    async def _connection(self):
+        return await aio_pika.connect_robust(self.url)
+
+    async def _channel(self, connection):
+        return await connection.channel()
+
+    async def _exchange(self, channel):
+        return await channel.declare_exchange(self.channel,
+                                              aio_pika.ExchangeType.FANOUT)
+
+    async def _queue(self, channel, exchange):
+        queue = await channel.declare_queue(durable=False,
+                                            arguments={'x-expires': 300000})
+        await queue.bind(exchange)
+        return queue
+
+    async def _publish(self, data):
+        connection = await self._connection()
+        channel = await self._channel(connection)
+        exchange = await self._exchange(channel)
+        await exchange.publish(
+            aio_pika.Message(body=pickle.dumps(data),
+                             delivery_mode=aio_pika.DeliveryMode.PERSISTENT),
+            routing_key='*'
+        )
+
+    async def _listen(self):
+        retry_sleep = 1
+        while True:
+            try:
+                if self.listener_connection is None:
+                    self.listener_connection = await self._connection()
+                    self.listener_channel = await self._channel(
+                        self.listener_connection
+                    )
+                    await self.listener_channel.set_qos(prefetch_count=1)
+                    exchange = await self._exchange(self.listener_channel)
+                    self.listener_queue = await self._queue(
+                        self.listener_channel, exchange
+                    )
+
+                async with self.listener_queue.iterator() as queue_iter:
+                    async for message in queue_iter:
+                        with message.process():
+                            return pickle.loads(message.body)
+            except Exception:
+                self._get_logger().error('Cannot receive from rabbitmq... '
+                                         'retrying in '
+                                         '{} secs'.format(retry_sleep))
+                self.listener_connection = None
+                await asyncio.sleep(retry_sleep)
+                retry_sleep *= 2
+                if retry_sleep > 60:
+                    retry_sleep = 60
diff --git a/libs/socketio/asyncio_client.py b/libs/socketio/asyncio_client.py
new file mode 100644
index 000000000..2b10434ae
--- /dev/null
+++ b/libs/socketio/asyncio_client.py
@@ -0,0 +1,475 @@
+import asyncio
+import logging
+import random
+
+import engineio
+import six
+
+from . import client
+from . import exceptions
+from . import packet
+
+default_logger = logging.getLogger('socketio.client')
+
+
+class AsyncClient(client.Client):
+    """A Socket.IO client for asyncio.
+
+    This class implements a fully compliant Socket.IO web client with support
+    for websocket and long-polling transports.
+
+    :param reconnection: ``True`` if the client should automatically attempt to
+                         reconnect to the server after an interruption, or
+                         ``False`` to not reconnect. The default is ``True``.
+    :param reconnection_attempts: How many reconnection attempts to issue
+                                  before giving up, or 0 for infinity attempts.
+                                  The default is 0.
+    :param reconnection_delay: How long to wait in seconds before the first
+                               reconnection attempt. Each successive attempt
+                               doubles this delay.
+    :param reconnection_delay_max: The maximum delay between reconnection
+                                   attempts.
+    :param randomization_factor: Randomization amount for each delay between
+                                 reconnection attempts. The default is 0.5,
+                                 which means that each delay is randomly
+                                 adjusted by +/- 50%.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param binary: ``True`` to support binary payloads, ``False`` to treat all
+                   payloads as text. On Python 2, if this is set to ``True``,
+                   ``unicode`` values are treated as text, and ``str`` and
+                   ``bytes`` values are treated as binary.  This option has no
+                   effect on Python 3, where text and binary payloads are
+                   always automatically discovered.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+
+    The Engine.IO configuration supports the following settings:
+
+    :param request_timeout: A timeout in seconds for requests. The default is
+                            5 seconds.
+    :param ssl_verify: ``True`` to verify SSL certificates, or ``False`` to
+                       skip SSL certificate verification, allowing
+                       connections to servers with self signed certificates.
+                       The default is ``True``.
+    :param engineio_logger: To enable Engine.IO logging set to ``True`` or pass
+                            a logger object to use. To disable logging set to
+                            ``False``. The default is ``False``.
+    """
+    def is_asyncio_based(self):
+        return True
+
+    async def connect(self, url, headers={}, transports=None,
+                      namespaces=None, socketio_path='socket.io'):
+        """Connect to a Socket.IO server.
+
+        :param url: The URL of the Socket.IO server. It can include custom
+                    query string parameters if required by the server.
+        :param headers: A dictionary with custom headers to send with the
+                        connection request.
+        :param transports: The list of allowed transports. Valid transports
+                           are ``'polling'`` and ``'websocket'``. If not
+                           given, the polling transport is connected first,
+                           then an upgrade to websocket is attempted.
+        :param namespaces: The list of custom namespaces to connect, in
+                           addition to the default namespace. If not given,
+                           the namespace list is obtained from the registered
+                           event handlers.
+        :param socketio_path: The endpoint where the Socket.IO server is
+                              installed. The default value is appropriate for
+                              most cases.
+
+        Note: this method is a coroutine.
+
+        Example usage::
+
+            sio = socketio.Client()
+            sio.connect('http://localhost:5000')
+        """
+        self.connection_url = url
+        self.connection_headers = headers
+        self.connection_transports = transports
+        self.connection_namespaces = namespaces
+        self.socketio_path = socketio_path
+
+        if namespaces is None:
+            namespaces = set(self.handlers.keys()).union(
+                set(self.namespace_handlers.keys()))
+        elif isinstance(namespaces, six.string_types):
+            namespaces = [namespaces]
+            self.connection_namespaces = namespaces
+        self.namespaces = [n for n in namespaces if n != '/']
+        try:
+            await self.eio.connect(url, headers=headers,
+                                   transports=transports,
+                                   engineio_path=socketio_path)
+        except engineio.exceptions.ConnectionError as exc:
+            six.raise_from(exceptions.ConnectionError(exc.args[0]), None)
+        self.connected = True
+
+    async def wait(self):
+        """Wait until the connection with the server ends.
+
+        Client applications can use this function to block the main thread
+        during the life of the connection.
+
+        Note: this method is a coroutine.
+        """
+        while True:
+            await self.eio.wait()
+            await self.sleep(1)  # give the reconnect task time to start up
+            if not self._reconnect_task:
+                break
+            await self._reconnect_task
+            if self.eio.state != 'connected':
+                break
+
+    async def emit(self, event, data=None, namespace=None, callback=None):
+        """Emit a custom event to one or more connected clients.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+
+        Note: this method is a coroutine.
+        """
+        namespace = namespace or '/'
+        if namespace != '/' and namespace not in self.namespaces:
+            raise exceptions.BadNamespaceError(
+                namespace + ' is not a connected namespace.')
+        self.logger.info('Emitting event "%s" [%s]', event, namespace)
+        if callback is not None:
+            id = self._generate_ack_id(namespace, callback)
+        else:
+            id = None
+        if six.PY2 and not self.binary:
+            binary = False  # pragma: nocover
+        else:
+            binary = None
+        # tuples are expanded to multiple arguments, everything else is sent
+        # as a single argument
+        if isinstance(data, tuple):
+            data = list(data)
+        elif data is not None:
+            data = [data]
+        else:
+            data = []
+        await self._send_packet(packet.Packet(
+            packet.EVENT, namespace=namespace, data=[event] + data, id=id,
+            binary=binary))
+
+    async def send(self, data, namespace=None, callback=None):
+        """Send a message to one or more connected clients.
+
+        This function emits an event with the name ``'message'``. Use
+        :func:`emit` to issue custom event names.
+
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+
+        Note: this method is a coroutine.
+        """
+        await self.emit('message', data=data, namespace=namespace,
+                        callback=callback)
+
+    async def call(self, event, data=None, namespace=None, timeout=60):
+        """Emit a custom event to a client and wait for the response.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param timeout: The waiting timeout. If the timeout is reached before
+                        the client acknowledges the event, then a
+                        ``TimeoutError`` exception is raised.
+
+        Note: this method is a coroutine.
+        """
+        callback_event = self.eio.create_event()
+        callback_args = []
+
+        def event_callback(*args):
+            callback_args.append(args)
+            callback_event.set()
+
+        await self.emit(event, data=data, namespace=namespace,
+                        callback=event_callback)
+        try:
+            await asyncio.wait_for(callback_event.wait(), timeout)
+        except asyncio.TimeoutError:
+            six.raise_from(exceptions.TimeoutError(), None)
+        return callback_args[0] if len(callback_args[0]) > 1 \
+            else callback_args[0][0] if len(callback_args[0]) == 1 \
+            else None
+
+    async def disconnect(self):
+        """Disconnect from the server.
+
+        Note: this method is a coroutine.
+        """
+        # here we just request the disconnection
+        # later in _handle_eio_disconnect we invoke the disconnect handler
+        for n in self.namespaces:
+            await self._send_packet(packet.Packet(packet.DISCONNECT,
+                                    namespace=n))
+        await self._send_packet(packet.Packet(
+            packet.DISCONNECT, namespace='/'))
+        self.connected = False
+        await self.eio.disconnect(abort=True)
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+        """
+        return self.eio.start_background_task(target, *args, **kwargs)
+
+    async def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+
+        Note: this method is a coroutine.
+        """
+        return await self.eio.sleep(seconds)
+
+    async def _send_packet(self, pkt):
+        """Send a Socket.IO packet to the server."""
+        encoded_packet = pkt.encode()
+        if isinstance(encoded_packet, list):
+            binary = False
+            for ep in encoded_packet:
+                await self.eio.send(ep, binary=binary)
+                binary = True
+        else:
+            await self.eio.send(encoded_packet, binary=False)
+
+    async def _handle_connect(self, namespace):
+        namespace = namespace or '/'
+        self.logger.info('Namespace {} is connected'.format(namespace))
+        await self._trigger_event('connect', namespace=namespace)
+        if namespace == '/':
+            for n in self.namespaces:
+                await self._send_packet(packet.Packet(packet.CONNECT,
+                                        namespace=n))
+        elif namespace not in self.namespaces:
+            self.namespaces.append(namespace)
+
+    async def _handle_disconnect(self, namespace):
+        if not self.connected:
+            return
+        namespace = namespace or '/'
+        if namespace == '/':
+            for n in self.namespaces:
+                await self._trigger_event('disconnect', namespace=n)
+            self.namespaces = []
+        await self._trigger_event('disconnect', namespace=namespace)
+        if namespace in self.namespaces:
+            self.namespaces.remove(namespace)
+        if namespace == '/':
+            self.connected = False
+
+    async def _handle_event(self, namespace, id, data):
+        namespace = namespace or '/'
+        self.logger.info('Received event "%s" [%s]', data[0], namespace)
+        r = await self._trigger_event(data[0], namespace, *data[1:])
+        if id is not None:
+            # send ACK packet with the response returned by the handler
+            # tuples are expanded as multiple arguments
+            if r is None:
+                data = []
+            elif isinstance(r, tuple):
+                data = list(r)
+            else:
+                data = [r]
+            if six.PY2 and not self.binary:
+                binary = False  # pragma: nocover
+            else:
+                binary = None
+            await self._send_packet(packet.Packet(
+                packet.ACK, namespace=namespace, id=id, data=data,
+                binary=binary))
+
+    async def _handle_ack(self, namespace, id, data):
+        namespace = namespace or '/'
+        self.logger.info('Received ack [%s]', namespace)
+        callback = None
+        try:
+            callback = self.callbacks[namespace][id]
+        except KeyError:
+            # if we get an unknown callback we just ignore it
+            self.logger.warning('Unknown callback received, ignoring.')
+        else:
+            del self.callbacks[namespace][id]
+        if callback is not None:
+            if asyncio.iscoroutinefunction(callback):
+                await callback(*data)
+            else:
+                callback(*data)
+
+    async def _handle_error(self, namespace, data):
+        namespace = namespace or '/'
+        self.logger.info('Connection to namespace {} was rejected'.format(
+            namespace))
+        if data is None:
+            data = tuple()
+        elif not isinstance(data, (tuple, list)):
+            data = (data,)
+        await self._trigger_event('connect_error', namespace, *data)
+        if namespace in self.namespaces:
+            self.namespaces.remove(namespace)
+        if namespace == '/':
+            self.namespaces = []
+            self.connected = False
+
+    async def _trigger_event(self, event, namespace, *args):
+        """Invoke an application event handler."""
+        # first see if we have an explicit handler for the event
+        if namespace in self.handlers and event in self.handlers[namespace]:
+            if asyncio.iscoroutinefunction(self.handlers[namespace][event]):
+                try:
+                    ret = await self.handlers[namespace][event](*args)
+                except asyncio.CancelledError:  # pragma: no cover
+                    ret = None
+            else:
+                ret = self.handlers[namespace][event](*args)
+            return ret
+
+        # or else, forward the event to a namepsace handler if one exists
+        elif namespace in self.namespace_handlers:
+            return await self.namespace_handlers[namespace].trigger_event(
+                event, *args)
+
+    async def _handle_reconnect(self):
+        self._reconnect_abort.clear()
+        client.reconnecting_clients.append(self)
+        attempt_count = 0
+        current_delay = self.reconnection_delay
+        while True:
+            delay = current_delay
+            current_delay *= 2
+            if delay > self.reconnection_delay_max:
+                delay = self.reconnection_delay_max
+            delay += self.randomization_factor * (2 * random.random() - 1)
+            self.logger.info(
+                'Connection failed, new attempt in {:.02f} seconds'.format(
+                    delay))
+            try:
+                await asyncio.wait_for(self._reconnect_abort.wait(), delay)
+                self.logger.info('Reconnect task aborted')
+                break
+            except (asyncio.TimeoutError, asyncio.CancelledError):
+                pass
+            attempt_count += 1
+            try:
+                await self.connect(self.connection_url,
+                                   headers=self.connection_headers,
+                                   transports=self.connection_transports,
+                                   namespaces=self.connection_namespaces,
+                                   socketio_path=self.socketio_path)
+            except (exceptions.ConnectionError, ValueError):
+                pass
+            else:
+                self.logger.info('Reconnection successful')
+                self._reconnect_task = None
+                break
+            if self.reconnection_attempts and \
+                    attempt_count >= self.reconnection_attempts:
+                self.logger.info(
+                    'Maximum reconnection attempts reached, giving up')
+                break
+        client.reconnecting_clients.remove(self)
+
+    def _handle_eio_connect(self):
+        """Handle the Engine.IO connection event."""
+        self.logger.info('Engine.IO connection established')
+        self.sid = self.eio.sid
+
+    async def _handle_eio_message(self, data):
+        """Dispatch Engine.IO messages."""
+        if self._binary_packet:
+            pkt = self._binary_packet
+            if pkt.add_attachment(data):
+                self._binary_packet = None
+                if pkt.packet_type == packet.BINARY_EVENT:
+                    await self._handle_event(pkt.namespace, pkt.id, pkt.data)
+                else:
+                    await self._handle_ack(pkt.namespace, pkt.id, pkt.data)
+        else:
+            pkt = packet.Packet(encoded_packet=data)
+            if pkt.packet_type == packet.CONNECT:
+                await self._handle_connect(pkt.namespace)
+            elif pkt.packet_type == packet.DISCONNECT:
+                await self._handle_disconnect(pkt.namespace)
+            elif pkt.packet_type == packet.EVENT:
+                await self._handle_event(pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.ACK:
+                await self._handle_ack(pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.BINARY_EVENT or \
+                    pkt.packet_type == packet.BINARY_ACK:
+                self._binary_packet = pkt
+            elif pkt.packet_type == packet.ERROR:
+                await self._handle_error(pkt.namespace, pkt.data)
+            else:
+                raise ValueError('Unknown packet type.')
+
+    async def _handle_eio_disconnect(self):
+        """Handle the Engine.IO disconnection event."""
+        self.logger.info('Engine.IO connection dropped')
+        self._reconnect_abort.set()
+        if self.connected:
+            for n in self.namespaces:
+                await self._trigger_event('disconnect', namespace=n)
+            await self._trigger_event('disconnect', namespace='/')
+            self.namespaces = []
+            self.connected = False
+        self.callbacks = {}
+        self._binary_packet = None
+        self.sid = None
+        if self.eio.state == 'connected' and self.reconnection:
+            self._reconnect_task = self.start_background_task(
+                self._handle_reconnect)
+
+    def _engineio_client_class(self):
+        return engineio.AsyncClient
diff --git a/libs/socketio/asyncio_manager.py b/libs/socketio/asyncio_manager.py
new file mode 100644
index 000000000..f4496ec7f
--- /dev/null
+++ b/libs/socketio/asyncio_manager.py
@@ -0,0 +1,58 @@
+import asyncio
+
+from .base_manager import BaseManager
+
+
+class AsyncManager(BaseManager):
+    """Manage a client list for an asyncio server."""
+    async def emit(self, event, data, namespace, room=None, skip_sid=None,
+                   callback=None, **kwargs):
+        """Emit a message to a single client, a room, or all the clients
+        connected to the namespace.
+
+        Note: this method is a coroutine.
+        """
+        if namespace not in self.rooms or room not in self.rooms[namespace]:
+            return
+        tasks = []
+        if not isinstance(skip_sid, list):
+            skip_sid = [skip_sid]
+        for sid in self.get_participants(namespace, room):
+            if sid not in skip_sid:
+                if callback is not None:
+                    id = self._generate_ack_id(sid, namespace, callback)
+                else:
+                    id = None
+                tasks.append(self.server._emit_internal(sid, event, data,
+                                                        namespace, id))
+        if tasks == []:  # pragma: no cover
+            return
+        await asyncio.wait(tasks)
+
+    async def close_room(self, room, namespace):
+        """Remove all participants from a room.
+
+        Note: this method is a coroutine.
+        """
+        return super().close_room(room, namespace)
+
+    async def trigger_callback(self, sid, namespace, id, data):
+        """Invoke an application callback.
+
+        Note: this method is a coroutine.
+        """
+        callback = None
+        try:
+            callback = self.callbacks[sid][namespace][id]
+        except KeyError:
+            # if we get an unknown callback we just ignore it
+            self._get_logger().warning('Unknown callback received, ignoring.')
+        else:
+            del self.callbacks[sid][namespace][id]
+        if callback is not None:
+            ret = callback(*data)
+            if asyncio.iscoroutine(ret):
+                try:
+                    await ret
+                except asyncio.CancelledError:  # pragma: no cover
+                    pass
diff --git a/libs/socketio/asyncio_namespace.py b/libs/socketio/asyncio_namespace.py
new file mode 100644
index 000000000..12e9c0fe6
--- /dev/null
+++ b/libs/socketio/asyncio_namespace.py
@@ -0,0 +1,204 @@
+import asyncio
+
+from socketio import namespace
+
+
+class AsyncNamespace(namespace.Namespace):
+    """Base class for asyncio server-side class-based namespaces.
+
+    A class-based namespace is a class that contains all the event handlers
+    for a Socket.IO namespace. The event handlers are methods of the class
+    with the prefix ``on_``, such as ``on_connect``, ``on_disconnect``,
+    ``on_message``, ``on_json``, and so on. These can be regular functions or
+    coroutines.
+
+    :param namespace: The Socket.IO namespace to be used with all the event
+                      handlers defined in this class. If this argument is
+                      omitted, the default namespace is used.
+    """
+    def is_asyncio_based(self):
+        return True
+
+    async def trigger_event(self, event, *args):
+        """Dispatch an event to the proper handler method.
+
+        In the most common usage, this method is not overloaded by subclasses,
+        as it performs the routing of events to methods. However, this
+        method can be overriden if special dispatching rules are needed, or if
+        having a single method that catches all events is desired.
+
+        Note: this method is a coroutine.
+        """
+        handler_name = 'on_' + event
+        if hasattr(self, handler_name):
+            handler = getattr(self, handler_name)
+            if asyncio.iscoroutinefunction(handler) is True:
+                try:
+                    ret = await handler(*args)
+                except asyncio.CancelledError:  # pragma: no cover
+                    ret = None
+            else:
+                ret = handler(*args)
+            return ret
+
+    async def emit(self, event, data=None, room=None, skip_sid=None,
+                   namespace=None, callback=None):
+        """Emit a custom event to one or more connected clients.
+
+        The only difference with the :func:`socketio.Server.emit` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.server.emit(event, data=data, room=room,
+                                      skip_sid=skip_sid,
+                                      namespace=namespace or self.namespace,
+                                      callback=callback)
+
+    async def send(self, data, room=None, skip_sid=None, namespace=None,
+                   callback=None):
+        """Send a message to one or more connected clients.
+
+        The only difference with the :func:`socketio.Server.send` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.server.send(data, room=room, skip_sid=skip_sid,
+                                      namespace=namespace or self.namespace,
+                                      callback=callback)
+
+    async def close_room(self, room, namespace=None):
+        """Close a room.
+
+        The only difference with the :func:`socketio.Server.close_room` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.server.close_room(
+            room, namespace=namespace or self.namespace)
+
+    async def get_session(self, sid, namespace=None):
+        """Return the user session for a client.
+
+        The only difference with the :func:`socketio.Server.get_session`
+        method is that when the ``namespace`` argument is not given the
+        namespace associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.server.get_session(
+            sid, namespace=namespace or self.namespace)
+
+    async def save_session(self, sid, session, namespace=None):
+        """Store the user session for a client.
+
+        The only difference with the :func:`socketio.Server.save_session`
+        method is that when the ``namespace`` argument is not given the
+        namespace associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.server.save_session(
+            sid, session, namespace=namespace or self.namespace)
+
+    def session(self, sid, namespace=None):
+        """Return the user session for a client with context manager syntax.
+
+        The only difference with the :func:`socketio.Server.session` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.session(sid, namespace=namespace or self.namespace)
+
+    async def disconnect(self, sid, namespace=None):
+        """Disconnect a client.
+
+        The only difference with the :func:`socketio.Server.disconnect` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.server.disconnect(
+            sid, namespace=namespace or self.namespace)
+
+
+class AsyncClientNamespace(namespace.ClientNamespace):
+    """Base class for asyncio client-side class-based namespaces.
+
+    A class-based namespace is a class that contains all the event handlers
+    for a Socket.IO namespace. The event handlers are methods of the class
+    with the prefix ``on_``, such as ``on_connect``, ``on_disconnect``,
+    ``on_message``, ``on_json``, and so on. These can be regular functions or
+    coroutines.
+
+    :param namespace: The Socket.IO namespace to be used with all the event
+                      handlers defined in this class. If this argument is
+                      omitted, the default namespace is used.
+    """
+    def is_asyncio_based(self):
+        return True
+
+    async def trigger_event(self, event, *args):
+        """Dispatch an event to the proper handler method.
+
+        In the most common usage, this method is not overloaded by subclasses,
+        as it performs the routing of events to methods. However, this
+        method can be overriden if special dispatching rules are needed, or if
+        having a single method that catches all events is desired.
+
+        Note: this method is a coroutine.
+        """
+        handler_name = 'on_' + event
+        if hasattr(self, handler_name):
+            handler = getattr(self, handler_name)
+            if asyncio.iscoroutinefunction(handler) is True:
+                try:
+                    ret = await handler(*args)
+                except asyncio.CancelledError:  # pragma: no cover
+                    ret = None
+            else:
+                ret = handler(*args)
+            return ret
+
+    async def emit(self, event, data=None, namespace=None, callback=None):
+        """Emit a custom event to the server.
+
+        The only difference with the :func:`socketio.Client.emit` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.client.emit(event, data=data,
+                                      namespace=namespace or self.namespace,
+                                      callback=callback)
+
+    async def send(self, data, namespace=None, callback=None):
+        """Send a message to the server.
+
+        The only difference with the :func:`socketio.Client.send` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.client.send(data,
+                                      namespace=namespace or self.namespace,
+                                      callback=callback)
+
+    async def disconnect(self):
+        """Disconnect a client.
+
+        The only difference with the :func:`socketio.Client.disconnect` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+
+        Note: this method is a coroutine.
+        """
+        return await self.client.disconnect()
diff --git a/libs/socketio/asyncio_pubsub_manager.py b/libs/socketio/asyncio_pubsub_manager.py
new file mode 100644
index 000000000..6fdba6d0c
--- /dev/null
+++ b/libs/socketio/asyncio_pubsub_manager.py
@@ -0,0 +1,163 @@
+from functools import partial
+import uuid
+
+import json
+import pickle
+import six
+
+from .asyncio_manager import AsyncManager
+
+
+class AsyncPubSubManager(AsyncManager):
+    """Manage a client list attached to a pub/sub backend under asyncio.
+
+    This is a base class that enables multiple servers to share the list of
+    clients, with the servers communicating events through a pub/sub backend.
+    The use of a pub/sub backend also allows any client connected to the
+    backend to emit events addressed to Socket.IO clients.
+
+    The actual backends must be implemented by subclasses, this class only
+    provides a pub/sub generic framework for asyncio applications.
+
+    :param channel: The channel name on which the server sends and receives
+                    notifications.
+    """
+    name = 'asyncpubsub'
+
+    def __init__(self, channel='socketio', write_only=False, logger=None):
+        super().__init__()
+        self.channel = channel
+        self.write_only = write_only
+        self.host_id = uuid.uuid4().hex
+        self.logger = logger
+
+    def initialize(self):
+        super().initialize()
+        if not self.write_only:
+            self.thread = self.server.start_background_task(self._thread)
+        self._get_logger().info(self.name + ' backend initialized.')
+
+    async def emit(self, event, data, namespace=None, room=None, skip_sid=None,
+                   callback=None, **kwargs):
+        """Emit a message to a single client, a room, or all the clients
+        connected to the namespace.
+
+        This method takes care or propagating the message to all the servers
+        that are connected through the message queue.
+
+        The parameters are the same as in :meth:`.Server.emit`.
+
+        Note: this method is a coroutine.
+        """
+        if kwargs.get('ignore_queue'):
+            return await super().emit(
+                event, data, namespace=namespace, room=room, skip_sid=skip_sid,
+                callback=callback)
+        namespace = namespace or '/'
+        if callback is not None:
+            if self.server is None:
+                raise RuntimeError('Callbacks can only be issued from the '
+                                   'context of a server.')
+            if room is None:
+                raise ValueError('Cannot use callback without a room set.')
+            id = self._generate_ack_id(room, namespace, callback)
+            callback = (room, namespace, id)
+        else:
+            callback = None
+        await self._publish({'method': 'emit', 'event': event, 'data': data,
+                             'namespace': namespace, 'room': room,
+                             'skip_sid': skip_sid, 'callback': callback,
+                             'host_id': self.host_id})
+
+    async def close_room(self, room, namespace=None):
+        await self._publish({'method': 'close_room', 'room': room,
+                             'namespace': namespace or '/'})
+
+    async def _publish(self, data):
+        """Publish a message on the Socket.IO channel.
+
+        This method needs to be implemented by the different subclasses that
+        support pub/sub backends.
+        """
+        raise NotImplementedError('This method must be implemented in a '
+                                  'subclass.')  # pragma: no cover
+
+    async def _listen(self):
+        """Return the next message published on the Socket.IO channel,
+        blocking until a message is available.
+
+        This method needs to be implemented by the different subclasses that
+        support pub/sub backends.
+        """
+        raise NotImplementedError('This method must be implemented in a '
+                                  'subclass.')  # pragma: no cover
+
+    async def _handle_emit(self, message):
+        # Events with callbacks are very tricky to handle across hosts
+        # Here in the receiving end we set up a local callback that preserves
+        # the callback host and id from the sender
+        remote_callback = message.get('callback')
+        remote_host_id = message.get('host_id')
+        if remote_callback is not None and len(remote_callback) == 3:
+            callback = partial(self._return_callback, remote_host_id,
+                               *remote_callback)
+        else:
+            callback = None
+        await super().emit(message['event'], message['data'],
+                           namespace=message.get('namespace'),
+                           room=message.get('room'),
+                           skip_sid=message.get('skip_sid'),
+                           callback=callback)
+
+    async def _handle_callback(self, message):
+        if self.host_id == message.get('host_id'):
+            try:
+                sid = message['sid']
+                namespace = message['namespace']
+                id = message['id']
+                args = message['args']
+            except KeyError:
+                return
+            await self.trigger_callback(sid, namespace, id, args)
+
+    async def _return_callback(self, host_id, sid, namespace, callback_id,
+                               *args):
+        # When an event callback is received, the callback is returned back
+        # the sender, which is identified by the host_id
+        await self._publish({'method': 'callback', 'host_id': host_id,
+                             'sid': sid, 'namespace': namespace,
+                             'id': callback_id, 'args': args})
+
+    async def _handle_close_room(self, message):
+        await super().close_room(
+            room=message.get('room'), namespace=message.get('namespace'))
+
+    async def _thread(self):
+        while True:
+            try:
+                message = await self._listen()
+            except:
+                import traceback
+                traceback.print_exc()
+                break
+            data = None
+            if isinstance(message, dict):
+                data = message
+            else:
+                if isinstance(message, six.binary_type):  # pragma: no cover
+                    try:
+                        data = pickle.loads(message)
+                    except:
+                        pass
+                if data is None:
+                    try:
+                        data = json.loads(message)
+                    except:
+                        pass
+            if data and 'method' in data:
+                if data['method'] == 'emit':
+                    await self._handle_emit(data)
+                elif data['method'] == 'callback':
+                    await self._handle_callback(data)
+                elif data['method'] == 'close_room':
+                    await self._handle_close_room(data)
diff --git a/libs/socketio/asyncio_redis_manager.py b/libs/socketio/asyncio_redis_manager.py
new file mode 100644
index 000000000..21499c26c
--- /dev/null
+++ b/libs/socketio/asyncio_redis_manager.py
@@ -0,0 +1,107 @@
+import asyncio
+import pickle
+from urllib.parse import urlparse
+
+try:
+    import aioredis
+except ImportError:
+    aioredis = None
+
+from .asyncio_pubsub_manager import AsyncPubSubManager
+
+
+def _parse_redis_url(url):
+    p = urlparse(url)
+    if p.scheme not in {'redis', 'rediss'}:
+        raise ValueError('Invalid redis url')
+    ssl = p.scheme == 'rediss'
+    host = p.hostname or 'localhost'
+    port = p.port or 6379
+    password = p.password
+    if p.path:
+        db = int(p.path[1:])
+    else:
+        db = 0
+    return host, port, password, db, ssl
+
+
+class AsyncRedisManager(AsyncPubSubManager):  # pragma: no cover
+    """Redis based client manager for asyncio servers.
+
+    This class implements a Redis backend for event sharing across multiple
+    processes. Only kept here as one more example of how to build a custom
+    backend, since the kombu backend is perfectly adequate to support a Redis
+    message queue.
+
+    To use a Redis backend, initialize the :class:`Server` instance as
+    follows::
+
+        server = socketio.Server(client_manager=socketio.AsyncRedisManager(
+            'redis://hostname:port/0'))
+
+    :param url: The connection URL for the Redis server. For a default Redis
+                store running on the same host, use ``redis://``.  To use an
+                SSL connection, use ``rediss://``.
+    :param channel: The channel name on which the server sends and receives
+                    notifications. Must be the same in all the servers.
+    :param write_only: If set ot ``True``, only initialize to emit events. The
+                       default of ``False`` initializes the class for emitting
+                       and receiving.
+    """
+    name = 'aioredis'
+
+    def __init__(self, url='redis://localhost:6379/0', channel='socketio',
+                 write_only=False, logger=None):
+        if aioredis is None:
+            raise RuntimeError('Redis package is not installed '
+                               '(Run "pip install aioredis" in your '
+                               'virtualenv).')
+        (
+            self.host, self.port, self.password, self.db, self.ssl
+        ) = _parse_redis_url(url)
+        self.pub = None
+        self.sub = None
+        super().__init__(channel=channel, write_only=write_only, logger=logger)
+
+    async def _publish(self, data):
+        retry = True
+        while True:
+            try:
+                if self.pub is None:
+                    self.pub = await aioredis.create_redis(
+                        (self.host, self.port), db=self.db,
+                        password=self.password, ssl=self.ssl
+                    )
+                return await self.pub.publish(self.channel,
+                                              pickle.dumps(data))
+            except (aioredis.RedisError, OSError):
+                if retry:
+                    self._get_logger().error('Cannot publish to redis... '
+                                             'retrying')
+                    self.pub = None
+                    retry = False
+                else:
+                    self._get_logger().error('Cannot publish to redis... '
+                                             'giving up')
+                    break
+
+    async def _listen(self):
+        retry_sleep = 1
+        while True:
+            try:
+                if self.sub is None:
+                    self.sub = await aioredis.create_redis(
+                        (self.host, self.port), db=self.db,
+                        password=self.password, ssl=self.ssl
+                    )
+                self.ch = (await self.sub.subscribe(self.channel))[0]
+                return await self.ch.get()
+            except (aioredis.RedisError, OSError):
+                self._get_logger().error('Cannot receive from redis... '
+                                         'retrying in '
+                                         '{} secs'.format(retry_sleep))
+                self.sub = None
+                await asyncio.sleep(retry_sleep)
+                retry_sleep *= 2
+                if retry_sleep > 60:
+                    retry_sleep = 60
diff --git a/libs/socketio/asyncio_server.py b/libs/socketio/asyncio_server.py
new file mode 100644
index 000000000..251d58180
--- /dev/null
+++ b/libs/socketio/asyncio_server.py
@@ -0,0 +1,526 @@
+import asyncio
+
+import engineio
+import six
+
+from . import asyncio_manager
+from . import exceptions
+from . import packet
+from . import server
+
+
+class AsyncServer(server.Server):
+    """A Socket.IO server for asyncio.
+
+    This class implements a fully compliant Socket.IO web server with support
+    for websocket and long-polling transports, compatible with the asyncio
+    framework on Python 3.5 or newer.
+
+    :param client_manager: The client manager instance that will manage the
+                           client list. When this is omitted, the client list
+                           is stored in an in-memory structure, so the use of
+                           multiple connected servers is not possible.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+    :param async_handlers: If set to ``True``, event handlers are executed in
+                           separate threads. To run handlers synchronously,
+                           set to ``False``. The default is ``True``.
+    :param kwargs: Connection parameters for the underlying Engine.IO server.
+
+    The Engine.IO configuration supports the following settings:
+
+    :param async_mode: The asynchronous model to use. See the Deployment
+                       section in the documentation for a description of the
+                       available options. Valid async modes are "aiohttp". If
+                       this argument is not given, an async mode is chosen
+                       based on the installed packages.
+    :param ping_timeout: The time in seconds that the client waits for the
+                         server to respond before disconnecting.
+    :param ping_interval: The interval in seconds at which the client pings
+                          the server.
+    :param max_http_buffer_size: The maximum size of a message when using the
+                                 polling transport.
+    :param allow_upgrades: Whether to allow transport upgrades or not.
+    :param http_compression: Whether to compress packages when using the
+                             polling transport.
+    :param compression_threshold: Only compress messages when their byte size
+                                  is greater than this value.
+    :param cookie: Name of the HTTP cookie that contains the client session
+                   id. If set to ``None``, a cookie is not sent to the client.
+    :param cors_allowed_origins: Origin or list of origins that are allowed to
+                                 connect to this server. Only the same origin
+                                 is allowed by default. Set this argument to
+                                 ``'*'`` to allow all origins, or to ``[]`` to
+                                 disable CORS handling.
+    :param cors_credentials: Whether credentials (cookies, authentication) are
+                             allowed in requests to this server.
+    :param monitor_clients: If set to ``True``, a background task will ensure
+                            inactive clients are closed. Set to ``False`` to
+                            disable the monitoring task (not recommended). The
+                            default is ``True``.
+    :param engineio_logger: To enable Engine.IO logging set to ``True`` or pass
+                            a logger object to use. To disable logging set to
+                            ``False``.
+    """
+    def __init__(self, client_manager=None, logger=False, json=None,
+                 async_handlers=True, **kwargs):
+        if client_manager is None:
+            client_manager = asyncio_manager.AsyncManager()
+        super().__init__(client_manager=client_manager, logger=logger,
+                         binary=False, json=json,
+                         async_handlers=async_handlers, **kwargs)
+
+    def is_asyncio_based(self):
+        return True
+
+    def attach(self, app, socketio_path='socket.io'):
+        """Attach the Socket.IO server to an application."""
+        self.eio.attach(app, socketio_path)
+
+    async def emit(self, event, data=None, to=None, room=None, skip_sid=None,
+                   namespace=None, callback=None, **kwargs):
+        """Emit a custom event to one or more connected clients.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param to: The recipient of the message. This can be set to the
+                   session ID of a client to address only that client, or to
+                   to any custom room created by the application to address all
+                   the clients in that room, If this argument is omitted the
+                   event is broadcasted to all connected clients.
+        :param room: Alias for the ``to`` parameter.
+        :param skip_sid: The session ID of a client to skip when broadcasting
+                         to a room or to all clients. This can be used to
+                         prevent a message from being sent to the sender.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+        :param ignore_queue: Only used when a message queue is configured. If
+                             set to ``True``, the event is emitted to the
+                             clients directly, without going through the queue.
+                             This is more efficient, but only works when a
+                             single server process is used. It is recommended
+                             to always leave this parameter with its default
+                             value of ``False``.
+
+        Note: this method is a coroutine.
+        """
+        namespace = namespace or '/'
+        room = to or room
+        self.logger.info('emitting event "%s" to %s [%s]', event,
+                         room or 'all', namespace)
+        await self.manager.emit(event, data, namespace, room=room,
+                                skip_sid=skip_sid, callback=callback,
+                                **kwargs)
+
+    async def send(self, data, to=None, room=None, skip_sid=None,
+                   namespace=None, callback=None, **kwargs):
+        """Send a message to one or more connected clients.
+
+        This function emits an event with the name ``'message'``. Use
+        :func:`emit` to issue custom event names.
+
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param to: The recipient of the message. This can be set to the
+                   session ID of a client to address only that client, or to
+                   to any custom room created by the application to address all
+                   the clients in that room, If this argument is omitted the
+                   event is broadcasted to all connected clients.
+        :param room: Alias for the ``to`` parameter.
+        :param skip_sid: The session ID of a client to skip when broadcasting
+                         to a room or to all clients. This can be used to
+                         prevent a message from being sent to the sender.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+        :param ignore_queue: Only used when a message queue is configured. If
+                             set to ``True``, the event is emitted to the
+                             clients directly, without going through the queue.
+                             This is more efficient, but only works when a
+                             single server process is used. It is recommended
+                             to always leave this parameter with its default
+                             value of ``False``.
+
+        Note: this method is a coroutine.
+        """
+        await self.emit('message', data=data, to=to, room=room,
+                        skip_sid=skip_sid, namespace=namespace,
+                        callback=callback, **kwargs)
+
+    async def call(self, event, data=None, to=None, sid=None, namespace=None,
+                   timeout=60, **kwargs):
+        """Emit a custom event to a client and wait for the response.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param to: The session ID of the recipient client.
+        :param sid: Alias for the ``to`` parameter.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param timeout: The waiting timeout. If the timeout is reached before
+                        the client acknowledges the event, then a
+                        ``TimeoutError`` exception is raised.
+        :param ignore_queue: Only used when a message queue is configured. If
+                             set to ``True``, the event is emitted to the
+                             client directly, without going through the queue.
+                             This is more efficient, but only works when a
+                             single server process is used. It is recommended
+                             to always leave this parameter with its default
+                             value of ``False``.
+        """
+        if not self.async_handlers:
+            raise RuntimeError(
+                'Cannot use call() when async_handlers is False.')
+        callback_event = self.eio.create_event()
+        callback_args = []
+
+        def event_callback(*args):
+            callback_args.append(args)
+            callback_event.set()
+
+        await self.emit(event, data=data, room=to or sid, namespace=namespace,
+                        callback=event_callback, **kwargs)
+        try:
+            await asyncio.wait_for(callback_event.wait(), timeout)
+        except asyncio.TimeoutError:
+            six.raise_from(exceptions.TimeoutError(), None)
+        return callback_args[0] if len(callback_args[0]) > 1 \
+            else callback_args[0][0] if len(callback_args[0]) == 1 \
+            else None
+
+    async def close_room(self, room, namespace=None):
+        """Close a room.
+
+        This function removes all the clients from the given room.
+
+        :param room: Room name.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the default namespace is used.
+
+        Note: this method is a coroutine.
+        """
+        namespace = namespace or '/'
+        self.logger.info('room %s is closing [%s]', room, namespace)
+        await self.manager.close_room(room, namespace)
+
+    async def get_session(self, sid, namespace=None):
+        """Return the user session for a client.
+
+        :param sid: The session id of the client.
+        :param namespace: The Socket.IO namespace. If this argument is omitted
+                          the default namespace is used.
+
+        The return value is a dictionary. Modifications made to this
+        dictionary are not guaranteed to be preserved. If you want to modify
+        the user session, use the ``session`` context manager instead.
+        """
+        namespace = namespace or '/'
+        eio_session = await self.eio.get_session(sid)
+        return eio_session.setdefault(namespace, {})
+
+    async def save_session(self, sid, session, namespace=None):
+        """Store the user session for a client.
+
+        :param sid: The session id of the client.
+        :param session: The session dictionary.
+        :param namespace: The Socket.IO namespace. If this argument is omitted
+                          the default namespace is used.
+        """
+        namespace = namespace or '/'
+        eio_session = await self.eio.get_session(sid)
+        eio_session[namespace] = session
+
+    def session(self, sid, namespace=None):
+        """Return the user session for a client with context manager syntax.
+
+        :param sid: The session id of the client.
+
+        This is a context manager that returns the user session dictionary for
+        the client. Any changes that are made to this dictionary inside the
+        context manager block are saved back to the session. Example usage::
+
+            @eio.on('connect')
+            def on_connect(sid, environ):
+                username = authenticate_user(environ)
+                if not username:
+                    return False
+                with eio.session(sid) as session:
+                    session['username'] = username
+
+            @eio.on('message')
+            def on_message(sid, msg):
+                async with eio.session(sid) as session:
+                    print('received message from ', session['username'])
+        """
+        class _session_context_manager(object):
+            def __init__(self, server, sid, namespace):
+                self.server = server
+                self.sid = sid
+                self.namespace = namespace
+                self.session = None
+
+            async def __aenter__(self):
+                self.session = await self.server.get_session(
+                    sid, namespace=self.namespace)
+                return self.session
+
+            async def __aexit__(self, *args):
+                await self.server.save_session(sid, self.session,
+                                               namespace=self.namespace)
+
+        return _session_context_manager(self, sid, namespace)
+
+    async def disconnect(self, sid, namespace=None):
+        """Disconnect a client.
+
+        :param sid: Session ID of the client.
+        :param namespace: The Socket.IO namespace to disconnect. If this
+                          argument is omitted the default namespace is used.
+
+        Note: this method is a coroutine.
+        """
+        namespace = namespace or '/'
+        if self.manager.is_connected(sid, namespace=namespace):
+            self.logger.info('Disconnecting %s [%s]', sid, namespace)
+            self.manager.pre_disconnect(sid, namespace=namespace)
+            await self._send_packet(sid, packet.Packet(packet.DISCONNECT,
+                                                       namespace=namespace))
+            await self._trigger_event('disconnect', namespace, sid)
+            self.manager.disconnect(sid, namespace=namespace)
+            if namespace == '/':
+                await self.eio.disconnect(sid)
+
+    async def handle_request(self, *args, **kwargs):
+        """Handle an HTTP request from the client.
+
+        This is the entry point of the Socket.IO application. This function
+        returns the HTTP response body to deliver to the client.
+
+        Note: this method is a coroutine.
+        """
+        return await self.eio.handle_request(*args, **kwargs)
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute. Must be a coroutine.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        The return value is a ``asyncio.Task`` object.
+
+        Note: this method is a coroutine.
+        """
+        return self.eio.start_background_task(target, *args, **kwargs)
+
+    async def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+
+        Note: this method is a coroutine.
+        """
+        return await self.eio.sleep(seconds)
+
+    async def _emit_internal(self, sid, event, data, namespace=None, id=None):
+        """Send a message to a client."""
+        # tuples are expanded to multiple arguments, everything else is sent
+        # as a single argument
+        if isinstance(data, tuple):
+            data = list(data)
+        else:
+            data = [data]
+        await self._send_packet(sid, packet.Packet(
+            packet.EVENT, namespace=namespace, data=[event] + data, id=id,
+            binary=None))
+
+    async def _send_packet(self, sid, pkt):
+        """Send a Socket.IO packet to a client."""
+        encoded_packet = pkt.encode()
+        if isinstance(encoded_packet, list):
+            binary = False
+            for ep in encoded_packet:
+                await self.eio.send(sid, ep, binary=binary)
+                binary = True
+        else:
+            await self.eio.send(sid, encoded_packet, binary=False)
+
+    async def _handle_connect(self, sid, namespace):
+        """Handle a client connection request."""
+        namespace = namespace or '/'
+        self.manager.connect(sid, namespace)
+        if self.always_connect:
+            await self._send_packet(sid, packet.Packet(packet.CONNECT,
+                                                       namespace=namespace))
+        fail_reason = None
+        try:
+            success = await self._trigger_event('connect', namespace, sid,
+                                                self.environ[sid])
+        except exceptions.ConnectionRefusedError as exc:
+            fail_reason = exc.error_args
+            success = False
+
+        if success is False:
+            if self.always_connect:
+                self.manager.pre_disconnect(sid, namespace)
+                await self._send_packet(sid, packet.Packet(
+                    packet.DISCONNECT, data=fail_reason, namespace=namespace))
+            self.manager.disconnect(sid, namespace)
+            if not self.always_connect:
+                await self._send_packet(sid, packet.Packet(
+                    packet.ERROR, data=fail_reason, namespace=namespace))
+            if sid in self.environ:  # pragma: no cover
+                del self.environ[sid]
+        elif not self.always_connect:
+            await self._send_packet(sid, packet.Packet(packet.CONNECT,
+                                                       namespace=namespace))
+
+    async def _handle_disconnect(self, sid, namespace):
+        """Handle a client disconnect."""
+        namespace = namespace or '/'
+        if namespace == '/':
+            namespace_list = list(self.manager.get_namespaces())
+        else:
+            namespace_list = [namespace]
+        for n in namespace_list:
+            if n != '/' and self.manager.is_connected(sid, n):
+                await self._trigger_event('disconnect', n, sid)
+                self.manager.disconnect(sid, n)
+        if namespace == '/' and self.manager.is_connected(sid, namespace):
+            await self._trigger_event('disconnect', '/', sid)
+            self.manager.disconnect(sid, '/')
+
+    async def _handle_event(self, sid, namespace, id, data):
+        """Handle an incoming client event."""
+        namespace = namespace or '/'
+        self.logger.info('received event "%s" from %s [%s]', data[0], sid,
+                         namespace)
+        if not self.manager.is_connected(sid, namespace):
+            self.logger.warning('%s is not connected to namespace %s',
+                                sid, namespace)
+            return
+        if self.async_handlers:
+            self.start_background_task(self._handle_event_internal, self, sid,
+                                       data, namespace, id)
+        else:
+            await self._handle_event_internal(self, sid, data, namespace, id)
+
+    async def _handle_event_internal(self, server, sid, data, namespace, id):
+        r = await server._trigger_event(data[0], namespace, sid, *data[1:])
+        if id is not None:
+            # send ACK packet with the response returned by the handler
+            # tuples are expanded as multiple arguments
+            if r is None:
+                data = []
+            elif isinstance(r, tuple):
+                data = list(r)
+            else:
+                data = [r]
+            await server._send_packet(sid, packet.Packet(packet.ACK,
+                                                         namespace=namespace,
+                                                         id=id, data=data,
+                                                         binary=None))
+
+    async def _handle_ack(self, sid, namespace, id, data):
+        """Handle ACK packets from the client."""
+        namespace = namespace or '/'
+        self.logger.info('received ack from %s [%s]', sid, namespace)
+        await self.manager.trigger_callback(sid, namespace, id, data)
+
+    async def _trigger_event(self, event, namespace, *args):
+        """Invoke an application event handler."""
+        # first see if we have an explicit handler for the event
+        if namespace in self.handlers and event in self.handlers[namespace]:
+            if asyncio.iscoroutinefunction(self.handlers[namespace][event]) \
+                    is True:
+                try:
+                    ret = await self.handlers[namespace][event](*args)
+                except asyncio.CancelledError:  # pragma: no cover
+                    ret = None
+            else:
+                ret = self.handlers[namespace][event](*args)
+            return ret
+
+        # or else, forward the event to a namepsace handler if one exists
+        elif namespace in self.namespace_handlers:
+            return await self.namespace_handlers[namespace].trigger_event(
+                event, *args)
+
+    async def _handle_eio_connect(self, sid, environ):
+        """Handle the Engine.IO connection event."""
+        if not self.manager_initialized:
+            self.manager_initialized = True
+            self.manager.initialize()
+        self.environ[sid] = environ
+        return await self._handle_connect(sid, '/')
+
+    async def _handle_eio_message(self, sid, data):
+        """Dispatch Engine.IO messages."""
+        if sid in self._binary_packet:
+            pkt = self._binary_packet[sid]
+            if pkt.add_attachment(data):
+                del self._binary_packet[sid]
+                if pkt.packet_type == packet.BINARY_EVENT:
+                    await self._handle_event(sid, pkt.namespace, pkt.id,
+                                             pkt.data)
+                else:
+                    await self._handle_ack(sid, pkt.namespace, pkt.id,
+                                           pkt.data)
+        else:
+            pkt = packet.Packet(encoded_packet=data)
+            if pkt.packet_type == packet.CONNECT:
+                await self._handle_connect(sid, pkt.namespace)
+            elif pkt.packet_type == packet.DISCONNECT:
+                await self._handle_disconnect(sid, pkt.namespace)
+            elif pkt.packet_type == packet.EVENT:
+                await self._handle_event(sid, pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.ACK:
+                await self._handle_ack(sid, pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.BINARY_EVENT or \
+                    pkt.packet_type == packet.BINARY_ACK:
+                self._binary_packet[sid] = pkt
+            elif pkt.packet_type == packet.ERROR:
+                raise ValueError('Unexpected ERROR packet.')
+            else:
+                raise ValueError('Unknown packet type.')
+
+    async def _handle_eio_disconnect(self, sid):
+        """Handle Engine.IO disconnect event."""
+        await self._handle_disconnect(sid, '/')
+        if sid in self.environ:
+            del self.environ[sid]
+
+    def _engineio_server_class(self):
+        return engineio.AsyncServer
diff --git a/libs/socketio/base_manager.py b/libs/socketio/base_manager.py
new file mode 100644
index 000000000..3cccb8569
--- /dev/null
+++ b/libs/socketio/base_manager.py
@@ -0,0 +1,178 @@
+import itertools
+import logging
+
+import six
+
+default_logger = logging.getLogger('socketio')
+
+
+class BaseManager(object):
+    """Manage client connections.
+
+    This class keeps track of all the clients and the rooms they are in, to
+    support the broadcasting of messages. The data used by this class is
+    stored in a memory structure, making it appropriate only for single process
+    services. More sophisticated storage backends can be implemented by
+    subclasses.
+    """
+    def __init__(self):
+        self.logger = None
+        self.server = None
+        self.rooms = {}
+        self.callbacks = {}
+        self.pending_disconnect = {}
+
+    def set_server(self, server):
+        self.server = server
+
+    def initialize(self):
+        """Invoked before the first request is received. Subclasses can add
+        their initialization code here.
+        """
+        pass
+
+    def get_namespaces(self):
+        """Return an iterable with the active namespace names."""
+        return six.iterkeys(self.rooms)
+
+    def get_participants(self, namespace, room):
+        """Return an iterable with the active participants in a room."""
+        for sid, active in six.iteritems(self.rooms[namespace][room].copy()):
+            yield sid
+
+    def connect(self, sid, namespace):
+        """Register a client connection to a namespace."""
+        self.enter_room(sid, namespace, None)
+        self.enter_room(sid, namespace, sid)
+
+    def is_connected(self, sid, namespace):
+        if namespace in self.pending_disconnect and \
+                sid in self.pending_disconnect[namespace]:
+            # the client is in the process of being disconnected
+            return False
+        try:
+            return self.rooms[namespace][None][sid]
+        except KeyError:
+            pass
+
+    def pre_disconnect(self, sid, namespace):
+        """Put the client in the to-be-disconnected list.
+
+        This allows the client data structures to be present while the
+        disconnect handler is invoked, but still recognize the fact that the
+        client is soon going away.
+        """
+        if namespace not in self.pending_disconnect:
+            self.pending_disconnect[namespace] = []
+        self.pending_disconnect[namespace].append(sid)
+
+    def disconnect(self, sid, namespace):
+        """Register a client disconnect from a namespace."""
+        if namespace not in self.rooms:
+            return
+        rooms = []
+        for room_name, room in six.iteritems(self.rooms[namespace].copy()):
+            if sid in room:
+                rooms.append(room_name)
+        for room in rooms:
+            self.leave_room(sid, namespace, room)
+        if sid in self.callbacks and namespace in self.callbacks[sid]:
+            del self.callbacks[sid][namespace]
+            if len(self.callbacks[sid]) == 0:
+                del self.callbacks[sid]
+        if namespace in self.pending_disconnect and \
+                sid in self.pending_disconnect[namespace]:
+            self.pending_disconnect[namespace].remove(sid)
+            if len(self.pending_disconnect[namespace]) == 0:
+                del self.pending_disconnect[namespace]
+
+    def enter_room(self, sid, namespace, room):
+        """Add a client to a room."""
+        if namespace not in self.rooms:
+            self.rooms[namespace] = {}
+        if room not in self.rooms[namespace]:
+            self.rooms[namespace][room] = {}
+        self.rooms[namespace][room][sid] = True
+
+    def leave_room(self, sid, namespace, room):
+        """Remove a client from a room."""
+        try:
+            del self.rooms[namespace][room][sid]
+            if len(self.rooms[namespace][room]) == 0:
+                del self.rooms[namespace][room]
+                if len(self.rooms[namespace]) == 0:
+                    del self.rooms[namespace]
+        except KeyError:
+            pass
+
+    def close_room(self, room, namespace):
+        """Remove all participants from a room."""
+        try:
+            for sid in self.get_participants(namespace, room):
+                self.leave_room(sid, namespace, room)
+        except KeyError:
+            pass
+
+    def get_rooms(self, sid, namespace):
+        """Return the rooms a client is in."""
+        r = []
+        try:
+            for room_name, room in six.iteritems(self.rooms[namespace]):
+                if room_name is not None and sid in room and room[sid]:
+                    r.append(room_name)
+        except KeyError:
+            pass
+        return r
+
+    def emit(self, event, data, namespace, room=None, skip_sid=None,
+             callback=None, **kwargs):
+        """Emit a message to a single client, a room, or all the clients
+        connected to the namespace."""
+        if namespace not in self.rooms or room not in self.rooms[namespace]:
+            return
+        if not isinstance(skip_sid, list):
+            skip_sid = [skip_sid]
+        for sid in self.get_participants(namespace, room):
+            if sid not in skip_sid:
+                if callback is not None:
+                    id = self._generate_ack_id(sid, namespace, callback)
+                else:
+                    id = None
+                self.server._emit_internal(sid, event, data, namespace, id)
+
+    def trigger_callback(self, sid, namespace, id, data):
+        """Invoke an application callback."""
+        callback = None
+        try:
+            callback = self.callbacks[sid][namespace][id]
+        except KeyError:
+            # if we get an unknown callback we just ignore it
+            self._get_logger().warning('Unknown callback received, ignoring.')
+        else:
+            del self.callbacks[sid][namespace][id]
+        if callback is not None:
+            callback(*data)
+
+    def _generate_ack_id(self, sid, namespace, callback):
+        """Generate a unique identifier for an ACK packet."""
+        namespace = namespace or '/'
+        if sid not in self.callbacks:
+            self.callbacks[sid] = {}
+        if namespace not in self.callbacks[sid]:
+            self.callbacks[sid][namespace] = {0: itertools.count(1)}
+        id = six.next(self.callbacks[sid][namespace][0])
+        self.callbacks[sid][namespace][id] = callback
+        return id
+
+    def _get_logger(self):
+        """Get the appropriate logger
+
+        Prevents uninitialized servers in write-only mode from failing.
+        """
+
+        if self.logger:
+            return self.logger
+        elif self.server:
+            return self.server.logger
+        else:
+            return default_logger
diff --git a/libs/socketio/client.py b/libs/socketio/client.py
new file mode 100644
index 000000000..e917d634d
--- /dev/null
+++ b/libs/socketio/client.py
@@ -0,0 +1,620 @@
+import itertools
+import logging
+import random
+import signal
+
+import engineio
+import six
+
+from . import exceptions
+from . import namespace
+from . import packet
+
+default_logger = logging.getLogger('socketio.client')
+reconnecting_clients = []
+
+
+def signal_handler(sig, frame):  # pragma: no cover
+    """SIGINT handler.
+
+    Notify any clients that are in a reconnect loop to abort. Other
+    disconnection tasks are handled at the engine.io level.
+    """
+    for client in reconnecting_clients[:]:
+        client._reconnect_abort.set()
+    return original_signal_handler(sig, frame)
+
+
+original_signal_handler = signal.signal(signal.SIGINT, signal_handler)
+
+
+class Client(object):
+    """A Socket.IO client.
+
+    This class implements a fully compliant Socket.IO web client with support
+    for websocket and long-polling transports.
+
+    :param reconnection: ``True`` if the client should automatically attempt to
+                         reconnect to the server after an interruption, or
+                         ``False`` to not reconnect. The default is ``True``.
+    :param reconnection_attempts: How many reconnection attempts to issue
+                                  before giving up, or 0 for infinity attempts.
+                                  The default is 0.
+    :param reconnection_delay: How long to wait in seconds before the first
+                               reconnection attempt. Each successive attempt
+                               doubles this delay.
+    :param reconnection_delay_max: The maximum delay between reconnection
+                                   attempts.
+    :param randomization_factor: Randomization amount for each delay between
+                                 reconnection attempts. The default is 0.5,
+                                 which means that each delay is randomly
+                                 adjusted by +/- 50%.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param binary: ``True`` to support binary payloads, ``False`` to treat all
+                   payloads as text. On Python 2, if this is set to ``True``,
+                   ``unicode`` values are treated as text, and ``str`` and
+                   ``bytes`` values are treated as binary.  This option has no
+                   effect on Python 3, where text and binary payloads are
+                   always automatically discovered.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+
+    The Engine.IO configuration supports the following settings:
+
+    :param request_timeout: A timeout in seconds for requests. The default is
+                            5 seconds.
+    :param ssl_verify: ``True`` to verify SSL certificates, or ``False`` to
+                       skip SSL certificate verification, allowing
+                       connections to servers with self signed certificates.
+                       The default is ``True``.
+    :param engineio_logger: To enable Engine.IO logging set to ``True`` or pass
+                            a logger object to use. To disable logging set to
+                            ``False``. The default is ``False``.
+    """
+    def __init__(self, reconnection=True, reconnection_attempts=0,
+                 reconnection_delay=1, reconnection_delay_max=5,
+                 randomization_factor=0.5, logger=False, binary=False,
+                 json=None, **kwargs):
+        self.reconnection = reconnection
+        self.reconnection_attempts = reconnection_attempts
+        self.reconnection_delay = reconnection_delay
+        self.reconnection_delay_max = reconnection_delay_max
+        self.randomization_factor = randomization_factor
+        self.binary = binary
+
+        engineio_options = kwargs
+        engineio_logger = engineio_options.pop('engineio_logger', None)
+        if engineio_logger is not None:
+            engineio_options['logger'] = engineio_logger
+        if json is not None:
+            packet.Packet.json = json
+            engineio_options['json'] = json
+
+        self.eio = self._engineio_client_class()(**engineio_options)
+        self.eio.on('connect', self._handle_eio_connect)
+        self.eio.on('message', self._handle_eio_message)
+        self.eio.on('disconnect', self._handle_eio_disconnect)
+
+        if not isinstance(logger, bool):
+            self.logger = logger
+        else:
+            self.logger = default_logger
+            if not logging.root.handlers and \
+                    self.logger.level == logging.NOTSET:
+                if logger:
+                    self.logger.setLevel(logging.INFO)
+                else:
+                    self.logger.setLevel(logging.ERROR)
+                self.logger.addHandler(logging.StreamHandler())
+
+        self.connection_url = None
+        self.connection_headers = None
+        self.connection_transports = None
+        self.connection_namespaces = None
+        self.socketio_path = None
+        self.sid = None
+
+        self.connected = False
+        self.namespaces = []
+        self.handlers = {}
+        self.namespace_handlers = {}
+        self.callbacks = {}
+        self._binary_packet = None
+        self._reconnect_task = None
+        self._reconnect_abort = self.eio.create_event()
+
+    def is_asyncio_based(self):
+        return False
+
+    def on(self, event, handler=None, namespace=None):
+        """Register an event handler.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param handler: The function that should be invoked to handle the
+                        event. When this parameter is not given, the method
+                        acts as a decorator for the handler function.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the handler is associated with
+                          the default namespace.
+
+        Example usage::
+
+            # as a decorator:
+            @sio.on('connect')
+            def connect_handler():
+                print('Connected!')
+
+            # as a method:
+            def message_handler(msg):
+                print('Received message: ', msg)
+                sio.send( 'response')
+            sio.on('message', message_handler)
+
+        The ``'connect'`` event handler receives no arguments. The
+        ``'message'`` handler and handlers for custom event names receive the
+        message payload as only argument. Any values returned from a message
+        handler will be passed to the client's acknowledgement callback
+        function if it exists. The ``'disconnect'`` handler does not take
+        arguments.
+        """
+        namespace = namespace or '/'
+
+        def set_handler(handler):
+            if namespace not in self.handlers:
+                self.handlers[namespace] = {}
+            self.handlers[namespace][event] = handler
+            return handler
+
+        if handler is None:
+            return set_handler
+        set_handler(handler)
+
+    def event(self, *args, **kwargs):
+        """Decorator to register an event handler.
+
+        This is a simplified version of the ``on()`` method that takes the
+        event name from the decorated function.
+
+        Example usage::
+
+            @sio.event
+            def my_event(data):
+                print('Received data: ', data)
+
+        The above example is equivalent to::
+
+            @sio.on('my_event')
+            def my_event(data):
+                print('Received data: ', data)
+
+        A custom namespace can be given as an argument to the decorator::
+
+            @sio.event(namespace='/test')
+            def my_event(data):
+                print('Received data: ', data)
+        """
+        if len(args) == 1 and len(kwargs) == 0 and callable(args[0]):
+            # the decorator was invoked without arguments
+            # args[0] is the decorated function
+            return self.on(args[0].__name__)(args[0])
+        else:
+            # the decorator was invoked with arguments
+            def set_handler(handler):
+                return self.on(handler.__name__, *args, **kwargs)(handler)
+
+            return set_handler
+
+    def register_namespace(self, namespace_handler):
+        """Register a namespace handler object.
+
+        :param namespace_handler: An instance of a :class:`Namespace`
+                                  subclass that handles all the event traffic
+                                  for a namespace.
+        """
+        if not isinstance(namespace_handler, namespace.ClientNamespace):
+            raise ValueError('Not a namespace instance')
+        if self.is_asyncio_based() != namespace_handler.is_asyncio_based():
+            raise ValueError('Not a valid namespace class for this client')
+        namespace_handler._set_client(self)
+        self.namespace_handlers[namespace_handler.namespace] = \
+            namespace_handler
+
+    def connect(self, url, headers={}, transports=None,
+                namespaces=None, socketio_path='socket.io'):
+        """Connect to a Socket.IO server.
+
+        :param url: The URL of the Socket.IO server. It can include custom
+                    query string parameters if required by the server.
+        :param headers: A dictionary with custom headers to send with the
+                        connection request.
+        :param transports: The list of allowed transports. Valid transports
+                           are ``'polling'`` and ``'websocket'``. If not
+                           given, the polling transport is connected first,
+                           then an upgrade to websocket is attempted.
+        :param namespaces: The list of custom namespaces to connect, in
+                           addition to the default namespace. If not given,
+                           the namespace list is obtained from the registered
+                           event handlers.
+        :param socketio_path: The endpoint where the Socket.IO server is
+                              installed. The default value is appropriate for
+                              most cases.
+
+        Example usage::
+
+            sio = socketio.Client()
+            sio.connect('http://localhost:5000')
+        """
+        self.connection_url = url
+        self.connection_headers = headers
+        self.connection_transports = transports
+        self.connection_namespaces = namespaces
+        self.socketio_path = socketio_path
+
+        if namespaces is None:
+            namespaces = set(self.handlers.keys()).union(
+                set(self.namespace_handlers.keys()))
+        elif isinstance(namespaces, six.string_types):
+            namespaces = [namespaces]
+            self.connection_namespaces = namespaces
+        self.namespaces = [n for n in namespaces if n != '/']
+        try:
+            self.eio.connect(url, headers=headers, transports=transports,
+                             engineio_path=socketio_path)
+        except engineio.exceptions.ConnectionError as exc:
+            six.raise_from(exceptions.ConnectionError(exc.args[0]), None)
+        self.connected = True
+
+    def wait(self):
+        """Wait until the connection with the server ends.
+
+        Client applications can use this function to block the main thread
+        during the life of the connection.
+        """
+        while True:
+            self.eio.wait()
+            self.sleep(1)  # give the reconnect task time to start up
+            if not self._reconnect_task:
+                break
+            self._reconnect_task.join()
+            if self.eio.state != 'connected':
+                break
+
+    def emit(self, event, data=None, namespace=None, callback=None):
+        """Emit a custom event to one or more connected clients.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+        """
+        namespace = namespace or '/'
+        if namespace != '/' and namespace not in self.namespaces:
+            raise exceptions.BadNamespaceError(
+                namespace + ' is not a connected namespace.')
+        self.logger.info('Emitting event "%s" [%s]', event, namespace)
+        if callback is not None:
+            id = self._generate_ack_id(namespace, callback)
+        else:
+            id = None
+        if six.PY2 and not self.binary:
+            binary = False  # pragma: nocover
+        else:
+            binary = None
+        # tuples are expanded to multiple arguments, everything else is sent
+        # as a single argument
+        if isinstance(data, tuple):
+            data = list(data)
+        elif data is not None:
+            data = [data]
+        else:
+            data = []
+        self._send_packet(packet.Packet(packet.EVENT, namespace=namespace,
+                                        data=[event] + data, id=id,
+                                        binary=binary))
+
+    def send(self, data, namespace=None, callback=None):
+        """Send a message to one or more connected clients.
+
+        This function emits an event with the name ``'message'``. Use
+        :func:`emit` to issue custom event names.
+
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+        """
+        self.emit('message', data=data, namespace=namespace,
+                  callback=callback)
+
+    def call(self, event, data=None, namespace=None, timeout=60):
+        """Emit a custom event to a client and wait for the response.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param timeout: The waiting timeout. If the timeout is reached before
+                        the client acknowledges the event, then a
+                        ``TimeoutError`` exception is raised.
+        """
+        callback_event = self.eio.create_event()
+        callback_args = []
+
+        def event_callback(*args):
+            callback_args.append(args)
+            callback_event.set()
+
+        self.emit(event, data=data, namespace=namespace,
+                  callback=event_callback)
+        if not callback_event.wait(timeout=timeout):
+            raise exceptions.TimeoutError()
+        return callback_args[0] if len(callback_args[0]) > 1 \
+            else callback_args[0][0] if len(callback_args[0]) == 1 \
+            else None
+
+    def disconnect(self):
+        """Disconnect from the server."""
+        # here we just request the disconnection
+        # later in _handle_eio_disconnect we invoke the disconnect handler
+        for n in self.namespaces:
+            self._send_packet(packet.Packet(packet.DISCONNECT, namespace=n))
+        self._send_packet(packet.Packet(
+            packet.DISCONNECT, namespace='/'))
+        self.connected = False
+        self.eio.disconnect(abort=True)
+
+    def transport(self):
+        """Return the name of the transport used by the client.
+
+        The two possible values returned by this function are ``'polling'``
+        and ``'websocket'``.
+        """
+        return self.eio.transport()
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+        """
+        return self.eio.start_background_task(target, *args, **kwargs)
+
+    def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+        """
+        return self.eio.sleep(seconds)
+
+    def _send_packet(self, pkt):
+        """Send a Socket.IO packet to the server."""
+        encoded_packet = pkt.encode()
+        if isinstance(encoded_packet, list):
+            binary = False
+            for ep in encoded_packet:
+                self.eio.send(ep, binary=binary)
+                binary = True
+        else:
+            self.eio.send(encoded_packet, binary=False)
+
+    def _generate_ack_id(self, namespace, callback):
+        """Generate a unique identifier for an ACK packet."""
+        namespace = namespace or '/'
+        if namespace not in self.callbacks:
+            self.callbacks[namespace] = {0: itertools.count(1)}
+        id = six.next(self.callbacks[namespace][0])
+        self.callbacks[namespace][id] = callback
+        return id
+
+    def _handle_connect(self, namespace):
+        namespace = namespace or '/'
+        self.logger.info('Namespace {} is connected'.format(namespace))
+        self._trigger_event('connect', namespace=namespace)
+        if namespace == '/':
+            for n in self.namespaces:
+                self._send_packet(packet.Packet(packet.CONNECT, namespace=n))
+        elif namespace not in self.namespaces:
+            self.namespaces.append(namespace)
+
+    def _handle_disconnect(self, namespace):
+        if not self.connected:
+            return
+        namespace = namespace or '/'
+        if namespace == '/':
+            for n in self.namespaces:
+                self._trigger_event('disconnect', namespace=n)
+            self.namespaces = []
+        self._trigger_event('disconnect', namespace=namespace)
+        if namespace in self.namespaces:
+            self.namespaces.remove(namespace)
+        if namespace == '/':
+            self.connected = False
+
+    def _handle_event(self, namespace, id, data):
+        namespace = namespace or '/'
+        self.logger.info('Received event "%s" [%s]', data[0], namespace)
+        r = self._trigger_event(data[0], namespace, *data[1:])
+        if id is not None:
+            # send ACK packet with the response returned by the handler
+            # tuples are expanded as multiple arguments
+            if r is None:
+                data = []
+            elif isinstance(r, tuple):
+                data = list(r)
+            else:
+                data = [r]
+            if six.PY2 and not self.binary:
+                binary = False  # pragma: nocover
+            else:
+                binary = None
+            self._send_packet(packet.Packet(packet.ACK, namespace=namespace,
+                              id=id, data=data, binary=binary))
+
+    def _handle_ack(self, namespace, id, data):
+        namespace = namespace or '/'
+        self.logger.info('Received ack [%s]', namespace)
+        callback = None
+        try:
+            callback = self.callbacks[namespace][id]
+        except KeyError:
+            # if we get an unknown callback we just ignore it
+            self.logger.warning('Unknown callback received, ignoring.')
+        else:
+            del self.callbacks[namespace][id]
+        if callback is not None:
+            callback(*data)
+
+    def _handle_error(self, namespace, data):
+        namespace = namespace or '/'
+        self.logger.info('Connection to namespace {} was rejected'.format(
+            namespace))
+        if data is None:
+            data = tuple()
+        elif not isinstance(data, (tuple, list)):
+            data = (data,)
+        self._trigger_event('connect_error', namespace, *data)
+        if namespace in self.namespaces:
+            self.namespaces.remove(namespace)
+        if namespace == '/':
+            self.namespaces = []
+            self.connected = False
+
+    def _trigger_event(self, event, namespace, *args):
+        """Invoke an application event handler."""
+        # first see if we have an explicit handler for the event
+        if namespace in self.handlers and event in self.handlers[namespace]:
+            return self.handlers[namespace][event](*args)
+
+        # or else, forward the event to a namespace handler if one exists
+        elif namespace in self.namespace_handlers:
+            return self.namespace_handlers[namespace].trigger_event(
+                event, *args)
+
+    def _handle_reconnect(self):
+        self._reconnect_abort.clear()
+        reconnecting_clients.append(self)
+        attempt_count = 0
+        current_delay = self.reconnection_delay
+        while True:
+            delay = current_delay
+            current_delay *= 2
+            if delay > self.reconnection_delay_max:
+                delay = self.reconnection_delay_max
+            delay += self.randomization_factor * (2 * random.random() - 1)
+            self.logger.info(
+                'Connection failed, new attempt in {:.02f} seconds'.format(
+                    delay))
+            if self._reconnect_abort.wait(delay):
+                self.logger.info('Reconnect task aborted')
+                break
+            attempt_count += 1
+            try:
+                self.connect(self.connection_url,
+                             headers=self.connection_headers,
+                             transports=self.connection_transports,
+                             namespaces=self.connection_namespaces,
+                             socketio_path=self.socketio_path)
+            except (exceptions.ConnectionError, ValueError):
+                pass
+            else:
+                self.logger.info('Reconnection successful')
+                self._reconnect_task = None
+                break
+            if self.reconnection_attempts and \
+                    attempt_count >= self.reconnection_attempts:
+                self.logger.info(
+                    'Maximum reconnection attempts reached, giving up')
+                break
+        reconnecting_clients.remove(self)
+
+    def _handle_eio_connect(self):
+        """Handle the Engine.IO connection event."""
+        self.logger.info('Engine.IO connection established')
+        self.sid = self.eio.sid
+
+    def _handle_eio_message(self, data):
+        """Dispatch Engine.IO messages."""
+        if self._binary_packet:
+            pkt = self._binary_packet
+            if pkt.add_attachment(data):
+                self._binary_packet = None
+                if pkt.packet_type == packet.BINARY_EVENT:
+                    self._handle_event(pkt.namespace, pkt.id, pkt.data)
+                else:
+                    self._handle_ack(pkt.namespace, pkt.id, pkt.data)
+        else:
+            pkt = packet.Packet(encoded_packet=data)
+            if pkt.packet_type == packet.CONNECT:
+                self._handle_connect(pkt.namespace)
+            elif pkt.packet_type == packet.DISCONNECT:
+                self._handle_disconnect(pkt.namespace)
+            elif pkt.packet_type == packet.EVENT:
+                self._handle_event(pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.ACK:
+                self._handle_ack(pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.BINARY_EVENT or \
+                    pkt.packet_type == packet.BINARY_ACK:
+                self._binary_packet = pkt
+            elif pkt.packet_type == packet.ERROR:
+                self._handle_error(pkt.namespace, pkt.data)
+            else:
+                raise ValueError('Unknown packet type.')
+
+    def _handle_eio_disconnect(self):
+        """Handle the Engine.IO disconnection event."""
+        self.logger.info('Engine.IO connection dropped')
+        if self.connected:
+            for n in self.namespaces:
+                self._trigger_event('disconnect', namespace=n)
+            self._trigger_event('disconnect', namespace='/')
+            self.namespaces = []
+            self.connected = False
+        self.callbacks = {}
+        self._binary_packet = None
+        self.sid = None
+        if self.eio.state == 'connected' and self.reconnection:
+            self._reconnect_task = self.start_background_task(
+                self._handle_reconnect)
+
+    def _engineio_client_class(self):
+        return engineio.Client
diff --git a/libs/socketio/exceptions.py b/libs/socketio/exceptions.py
new file mode 100644
index 000000000..36dddd9fc
--- /dev/null
+++ b/libs/socketio/exceptions.py
@@ -0,0 +1,30 @@
+class SocketIOError(Exception):
+    pass
+
+
+class ConnectionError(SocketIOError):
+    pass
+
+
+class ConnectionRefusedError(ConnectionError):
+    """Connection refused exception.
+
+    This exception can be raised from a connect handler when the connection
+    is not accepted. The positional arguments provided with the exception are
+    returned with the error packet to the client.
+    """
+    def __init__(self, *args):
+        if len(args) == 0:
+            self.error_args = None
+        elif len(args) == 1 and not isinstance(args[0], list):
+            self.error_args = args[0]
+        else:
+            self.error_args = args
+
+
+class TimeoutError(SocketIOError):
+    pass
+
+
+class BadNamespaceError(SocketIOError):
+    pass
diff --git a/libs/socketio/kafka_manager.py b/libs/socketio/kafka_manager.py
new file mode 100644
index 000000000..00a2e7f05
--- /dev/null
+++ b/libs/socketio/kafka_manager.py
@@ -0,0 +1,63 @@
+import logging
+import pickle
+
+try:
+    import kafka
+except ImportError:
+    kafka = None
+
+from .pubsub_manager import PubSubManager
+
+logger = logging.getLogger('socketio')
+
+
+class KafkaManager(PubSubManager):  # pragma: no cover
+    """Kafka based client manager.
+
+    This class implements a Kafka backend for event sharing across multiple
+    processes.
+
+    To use a Kafka backend, initialize the :class:`Server` instance as
+    follows::
+
+        url = 'kafka://hostname:port'
+        server = socketio.Server(client_manager=socketio.KafkaManager(url))
+
+    :param url: The connection URL for the Kafka server. For a default Kafka
+                store running on the same host, use ``kafka://``.
+    :param channel: The channel name (topic) on which the server sends and
+                    receives notifications. Must be the same in all the
+                    servers.
+    :param write_only: If set ot ``True``, only initialize to emit events. The
+                       default of ``False`` initializes the class for emitting
+                       and receiving.
+    """
+    name = 'kafka'
+
+    def __init__(self, url='kafka://localhost:9092', channel='socketio',
+                 write_only=False):
+        if kafka is None:
+            raise RuntimeError('kafka-python package is not installed '
+                               '(Run "pip install kafka-python" in your '
+                               'virtualenv).')
+
+        super(KafkaManager, self).__init__(channel=channel,
+                                           write_only=write_only)
+
+        self.kafka_url = url[8:] if url != 'kafka://' else 'localhost:9092'
+        self.producer = kafka.KafkaProducer(bootstrap_servers=self.kafka_url)
+        self.consumer = kafka.KafkaConsumer(self.channel,
+                                            bootstrap_servers=self.kafka_url)
+
+    def _publish(self, data):
+        self.producer.send(self.channel, value=pickle.dumps(data))
+        self.producer.flush()
+
+    def _kafka_listen(self):
+        for message in self.consumer:
+            yield message
+
+    def _listen(self):
+        for message in self._kafka_listen():
+            if message.topic == self.channel:
+                yield pickle.loads(message.value)
diff --git a/libs/socketio/kombu_manager.py b/libs/socketio/kombu_manager.py
new file mode 100644
index 000000000..4eb9ee498
--- /dev/null
+++ b/libs/socketio/kombu_manager.py
@@ -0,0 +1,122 @@
+import pickle
+import uuid
+
+try:
+    import kombu
+except ImportError:
+    kombu = None
+
+from .pubsub_manager import PubSubManager
+
+
+class KombuManager(PubSubManager):  # pragma: no cover
+    """Client manager that uses kombu for inter-process messaging.
+
+    This class implements a client manager backend for event sharing across
+    multiple processes, using RabbitMQ, Redis or any other messaging mechanism
+    supported by `kombu <http://kombu.readthedocs.org/en/latest/>`_.
+
+    To use a kombu backend, initialize the :class:`Server` instance as
+    follows::
+
+        url = 'amqp://user:password@hostname:port//'
+        server = socketio.Server(client_manager=socketio.KombuManager(url))
+
+    :param url: The connection URL for the backend messaging queue. Example
+                connection URLs are ``'amqp://guest:guest@localhost:5672//'``
+                and ``'redis://localhost:6379/'`` for RabbitMQ and Redis
+                respectively. Consult the `kombu documentation
+                <http://kombu.readthedocs.org/en/latest/userguide\
+                /connections.html#urls>`_ for more on how to construct
+                connection URLs.
+    :param channel: The channel name on which the server sends and receives
+                    notifications. Must be the same in all the servers.
+    :param write_only: If set ot ``True``, only initialize to emit events. The
+                       default of ``False`` initializes the class for emitting
+                       and receiving.
+    :param connection_options: additional keyword arguments to be passed to
+                               ``kombu.Connection()``.
+    :param exchange_options: additional keyword arguments to be passed to
+                             ``kombu.Exchange()``.
+    :param queue_options: additional keyword arguments to be passed to
+                          ``kombu.Queue()``.
+    :param producer_options: additional keyword arguments to be passed to
+                             ``kombu.Producer()``.
+    """
+    name = 'kombu'
+
+    def __init__(self, url='amqp://guest:guest@localhost:5672//',
+                 channel='socketio', write_only=False, logger=None,
+                 connection_options=None, exchange_options=None,
+                 queue_options=None, producer_options=None):
+        if kombu is None:
+            raise RuntimeError('Kombu package is not installed '
+                               '(Run "pip install kombu" in your '
+                               'virtualenv).')
+        super(KombuManager, self).__init__(channel=channel,
+                                           write_only=write_only,
+                                           logger=logger)
+        self.url = url
+        self.connection_options = connection_options or {}
+        self.exchange_options = exchange_options or {}
+        self.queue_options = queue_options or {}
+        self.producer_options = producer_options or {}
+        self.producer = self._producer()
+
+    def initialize(self):
+        super(KombuManager, self).initialize()
+
+        monkey_patched = True
+        if self.server.async_mode == 'eventlet':
+            from eventlet.patcher import is_monkey_patched
+            monkey_patched = is_monkey_patched('socket')
+        elif 'gevent' in self.server.async_mode:
+            from gevent.monkey import is_module_patched
+            monkey_patched = is_module_patched('socket')
+        if not monkey_patched:
+            raise RuntimeError(
+                'Kombu requires a monkey patched socket library to work '
+                'with ' + self.server.async_mode)
+
+    def _connection(self):
+        return kombu.Connection(self.url, **self.connection_options)
+
+    def _exchange(self):
+        options = {'type': 'fanout', 'durable': False}
+        options.update(self.exchange_options)
+        return kombu.Exchange(self.channel, **options)
+
+    def _queue(self):
+        queue_name = 'flask-socketio.' + str(uuid.uuid4())
+        options = {'durable': False, 'queue_arguments': {'x-expires': 300000}}
+        options.update(self.queue_options)
+        return kombu.Queue(queue_name, self._exchange(), **options)
+
+    def _producer(self):
+        return self._connection().Producer(exchange=self._exchange(),
+                                           **self.producer_options)
+
+    def __error_callback(self, exception, interval):
+        self._get_logger().exception('Sleeping {}s'.format(interval))
+
+    def _publish(self, data):
+        connection = self._connection()
+        publish = connection.ensure(self.producer, self.producer.publish,
+                                    errback=self.__error_callback)
+        publish(pickle.dumps(data))
+
+    def _listen(self):
+        reader_queue = self._queue()
+
+        while True:
+            connection = self._connection().ensure_connection(
+                errback=self.__error_callback)
+            try:
+                with connection.SimpleQueue(reader_queue) as queue:
+                    while True:
+                        message = queue.get(block=True)
+                        message.ack()
+                        yield message.payload
+            except connection.connection_errors:
+                self._get_logger().exception("Connection error "
+                                             "while reading from queue")
diff --git a/libs/socketio/middleware.py b/libs/socketio/middleware.py
new file mode 100644
index 000000000..1a6974085
--- /dev/null
+++ b/libs/socketio/middleware.py
@@ -0,0 +1,42 @@
+import engineio
+
+
+class WSGIApp(engineio.WSGIApp):
+    """WSGI middleware for Socket.IO.
+
+    This middleware dispatches traffic to a Socket.IO application. It can also
+    serve a list of static files to the client, or forward unrelated HTTP
+    traffic to another WSGI application.
+
+    :param socketio_app: The Socket.IO server. Must be an instance of the
+                         ``socketio.Server`` class.
+    :param wsgi_app: The WSGI app that receives all other traffic.
+    :param static_files: A dictionary with static file mapping rules. See the
+                         documentation for details on this argument.
+    :param socketio_path: The endpoint where the Socket.IO application should
+                          be installed. The default value is appropriate for
+                          most cases.
+
+    Example usage::
+
+        import socketio
+        import eventlet
+        from . import wsgi_app
+
+        sio = socketio.Server()
+        app = socketio.WSGIApp(sio, wsgi_app)
+        eventlet.wsgi.server(eventlet.listen(('', 8000)), app)
+    """
+    def __init__(self, socketio_app, wsgi_app=None, static_files=None,
+                 socketio_path='socket.io'):
+        super(WSGIApp, self).__init__(socketio_app, wsgi_app,
+                                      static_files=static_files,
+                                      engineio_path=socketio_path)
+
+
+class Middleware(WSGIApp):
+    """This class has been renamed to WSGIApp and is now deprecated."""
+    def __init__(self, socketio_app, wsgi_app=None,
+                 socketio_path='socket.io'):
+        super(Middleware, self).__init__(socketio_app, wsgi_app,
+                                         socketio_path=socketio_path)
diff --git a/libs/socketio/namespace.py b/libs/socketio/namespace.py
new file mode 100644
index 000000000..418615ff8
--- /dev/null
+++ b/libs/socketio/namespace.py
@@ -0,0 +1,191 @@
+class BaseNamespace(object):
+    def __init__(self, namespace=None):
+        self.namespace = namespace or '/'
+
+    def is_asyncio_based(self):
+        return False
+
+    def trigger_event(self, event, *args):
+        """Dispatch an event to the proper handler method.
+
+        In the most common usage, this method is not overloaded by subclasses,
+        as it performs the routing of events to methods. However, this
+        method can be overriden if special dispatching rules are needed, or if
+        having a single method that catches all events is desired.
+        """
+        handler_name = 'on_' + event
+        if hasattr(self, handler_name):
+            return getattr(self, handler_name)(*args)
+
+
+class Namespace(BaseNamespace):
+    """Base class for server-side class-based namespaces.
+
+    A class-based namespace is a class that contains all the event handlers
+    for a Socket.IO namespace. The event handlers are methods of the class
+    with the prefix ``on_``, such as ``on_connect``, ``on_disconnect``,
+    ``on_message``, ``on_json``, and so on.
+
+    :param namespace: The Socket.IO namespace to be used with all the event
+                      handlers defined in this class. If this argument is
+                      omitted, the default namespace is used.
+    """
+    def __init__(self, namespace=None):
+        super(Namespace, self).__init__(namespace=namespace)
+        self.server = None
+
+    def _set_server(self, server):
+        self.server = server
+
+    def emit(self, event, data=None, room=None, skip_sid=None, namespace=None,
+             callback=None):
+        """Emit a custom event to one or more connected clients.
+
+        The only difference with the :func:`socketio.Server.emit` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.emit(event, data=data, room=room, skip_sid=skip_sid,
+                                namespace=namespace or self.namespace,
+                                callback=callback)
+
+    def send(self, data, room=None, skip_sid=None, namespace=None,
+             callback=None):
+        """Send a message to one or more connected clients.
+
+        The only difference with the :func:`socketio.Server.send` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.send(data, room=room, skip_sid=skip_sid,
+                                namespace=namespace or self.namespace,
+                                callback=callback)
+
+    def enter_room(self, sid, room, namespace=None):
+        """Enter a room.
+
+        The only difference with the :func:`socketio.Server.enter_room` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.enter_room(sid, room,
+                                      namespace=namespace or self.namespace)
+
+    def leave_room(self, sid, room, namespace=None):
+        """Leave a room.
+
+        The only difference with the :func:`socketio.Server.leave_room` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.leave_room(sid, room,
+                                      namespace=namespace or self.namespace)
+
+    def close_room(self, room, namespace=None):
+        """Close a room.
+
+        The only difference with the :func:`socketio.Server.close_room` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.close_room(room,
+                                      namespace=namespace or self.namespace)
+
+    def rooms(self, sid, namespace=None):
+        """Return the rooms a client is in.
+
+        The only difference with the :func:`socketio.Server.rooms` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.rooms(sid, namespace=namespace or self.namespace)
+
+    def get_session(self, sid, namespace=None):
+        """Return the user session for a client.
+
+        The only difference with the :func:`socketio.Server.get_session`
+        method is that when the ``namespace`` argument is not given the
+        namespace associated with the class is used.
+        """
+        return self.server.get_session(
+            sid, namespace=namespace or self.namespace)
+
+    def save_session(self, sid, session, namespace=None):
+        """Store the user session for a client.
+
+        The only difference with the :func:`socketio.Server.save_session`
+        method is that when the ``namespace`` argument is not given the
+        namespace associated with the class is used.
+        """
+        return self.server.save_session(
+            sid, session, namespace=namespace or self.namespace)
+
+    def session(self, sid, namespace=None):
+        """Return the user session for a client with context manager syntax.
+
+        The only difference with the :func:`socketio.Server.session` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.session(sid, namespace=namespace or self.namespace)
+
+    def disconnect(self, sid, namespace=None):
+        """Disconnect a client.
+
+        The only difference with the :func:`socketio.Server.disconnect` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.server.disconnect(sid,
+                                      namespace=namespace or self.namespace)
+
+
+class ClientNamespace(BaseNamespace):
+    """Base class for client-side class-based namespaces.
+
+    A class-based namespace is a class that contains all the event handlers
+    for a Socket.IO namespace. The event handlers are methods of the class
+    with the prefix ``on_``, such as ``on_connect``, ``on_disconnect``,
+    ``on_message``, ``on_json``, and so on.
+
+    :param namespace: The Socket.IO namespace to be used with all the event
+                      handlers defined in this class. If this argument is
+                      omitted, the default namespace is used.
+    """
+    def __init__(self, namespace=None):
+        super(ClientNamespace, self).__init__(namespace=namespace)
+        self.client = None
+
+    def _set_client(self, client):
+        self.client = client
+
+    def emit(self, event, data=None, namespace=None, callback=None):
+        """Emit a custom event to the server.
+
+        The only difference with the :func:`socketio.Client.emit` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.client.emit(event, data=data,
+                                namespace=namespace or self.namespace,
+                                callback=callback)
+
+    def send(self, data, room=None, skip_sid=None, namespace=None,
+             callback=None):
+        """Send a message to the server.
+
+        The only difference with the :func:`socketio.Client.send` method is
+        that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.client.send(data, namespace=namespace or self.namespace,
+                                callback=callback)
+
+    def disconnect(self):
+        """Disconnect from the server.
+
+        The only difference with the :func:`socketio.Client.disconnect` method
+        is that when the ``namespace`` argument is not given the namespace
+        associated with the class is used.
+        """
+        return self.client.disconnect()
diff --git a/libs/socketio/packet.py b/libs/socketio/packet.py
new file mode 100644
index 000000000..73b469d6d
--- /dev/null
+++ b/libs/socketio/packet.py
@@ -0,0 +1,179 @@
+import functools
+import json as _json
+
+import six
+
+(CONNECT, DISCONNECT, EVENT, ACK, ERROR, BINARY_EVENT, BINARY_ACK) = \
+    (0, 1, 2, 3, 4, 5, 6)
+packet_names = ['CONNECT', 'DISCONNECT', 'EVENT', 'ACK', 'ERROR',
+                'BINARY_EVENT', 'BINARY_ACK']
+
+
+class Packet(object):
+    """Socket.IO packet."""
+
+    # the format of the Socket.IO packet is as follows:
+    #
+    # packet type: 1 byte, values 0-6
+    # num_attachments: ASCII encoded, only if num_attachments != 0
+    # '-': only if num_attachments != 0
+    # namespace: only if namespace != '/'
+    # ',': only if namespace and one of id and data are defined in this packet
+    # id: ASCII encoded, only if id is not None
+    # data: JSON dump of data payload
+
+    json = _json
+
+    def __init__(self, packet_type=EVENT, data=None, namespace=None, id=None,
+                 binary=None, encoded_packet=None):
+        self.packet_type = packet_type
+        self.data = data
+        self.namespace = namespace
+        self.id = id
+        if binary or (binary is None and self._data_is_binary(self.data)):
+            if self.packet_type == EVENT:
+                self.packet_type = BINARY_EVENT
+            elif self.packet_type == ACK:
+                self.packet_type = BINARY_ACK
+            else:
+                raise ValueError('Packet does not support binary payload.')
+        self.attachment_count = 0
+        self.attachments = []
+        if encoded_packet:
+            self.attachment_count = self.decode(encoded_packet)
+
+    def encode(self):
+        """Encode the packet for transmission.
+
+        If the packet contains binary elements, this function returns a list
+        of packets where the first is the original packet with placeholders for
+        the binary components and the remaining ones the binary attachments.
+        """
+        encoded_packet = six.text_type(self.packet_type)
+        if self.packet_type == BINARY_EVENT or self.packet_type == BINARY_ACK:
+            data, attachments = self._deconstruct_binary(self.data)
+            encoded_packet += six.text_type(len(attachments)) + '-'
+        else:
+            data = self.data
+            attachments = None
+        needs_comma = False
+        if self.namespace is not None and self.namespace != '/':
+            encoded_packet += self.namespace
+            needs_comma = True
+        if self.id is not None:
+            if needs_comma:
+                encoded_packet += ','
+                needs_comma = False
+            encoded_packet += six.text_type(self.id)
+        if data is not None:
+            if needs_comma:
+                encoded_packet += ','
+            encoded_packet += self.json.dumps(data, separators=(',', ':'))
+        if attachments is not None:
+            encoded_packet = [encoded_packet] + attachments
+        return encoded_packet
+
+    def decode(self, encoded_packet):
+        """Decode a transmitted package.
+
+        The return value indicates how many binary attachment packets are
+        necessary to fully decode the packet.
+        """
+        ep = encoded_packet
+        try:
+            self.packet_type = int(ep[0:1])
+        except TypeError:
+            self.packet_type = ep
+            ep = ''
+        self.namespace = None
+        self.data = None
+        ep = ep[1:]
+        dash = ep.find('-')
+        attachment_count = 0
+        if dash > 0 and ep[0:dash].isdigit():
+            attachment_count = int(ep[0:dash])
+            ep = ep[dash + 1:]
+        if ep and ep[0:1] == '/':
+            sep = ep.find(',')
+            if sep == -1:
+                self.namespace = ep
+                ep = ''
+            else:
+                self.namespace = ep[0:sep]
+                ep = ep[sep + 1:]
+            q = self.namespace.find('?')
+            if q != -1:
+                self.namespace = self.namespace[0:q]
+        if ep and ep[0].isdigit():
+            self.id = 0
+            while ep and ep[0].isdigit():
+                self.id = self.id * 10 + int(ep[0])
+                ep = ep[1:]
+        if ep:
+            self.data = self.json.loads(ep)
+        return attachment_count
+
+    def add_attachment(self, attachment):
+        if self.attachment_count <= len(self.attachments):
+            raise ValueError('Unexpected binary attachment')
+        self.attachments.append(attachment)
+        if self.attachment_count == len(self.attachments):
+            self.reconstruct_binary(self.attachments)
+            return True
+        return False
+
+    def reconstruct_binary(self, attachments):
+        """Reconstruct a decoded packet using the given list of binary
+        attachments.
+        """
+        self.data = self._reconstruct_binary_internal(self.data,
+                                                      self.attachments)
+
+    def _reconstruct_binary_internal(self, data, attachments):
+        if isinstance(data, list):
+            return [self._reconstruct_binary_internal(item, attachments)
+                    for item in data]
+        elif isinstance(data, dict):
+            if data.get('_placeholder') and 'num' in data:
+                return attachments[data['num']]
+            else:
+                return {key: self._reconstruct_binary_internal(value,
+                                                               attachments)
+                        for key, value in six.iteritems(data)}
+        else:
+            return data
+
+    def _deconstruct_binary(self, data):
+        """Extract binary components in the packet."""
+        attachments = []
+        data = self._deconstruct_binary_internal(data, attachments)
+        return data, attachments
+
+    def _deconstruct_binary_internal(self, data, attachments):
+        if isinstance(data, six.binary_type):
+            attachments.append(data)
+            return {'_placeholder': True, 'num': len(attachments) - 1}
+        elif isinstance(data, list):
+            return [self._deconstruct_binary_internal(item, attachments)
+                    for item in data]
+        elif isinstance(data, dict):
+            return {key: self._deconstruct_binary_internal(value, attachments)
+                    for key, value in six.iteritems(data)}
+        else:
+            return data
+
+    def _data_is_binary(self, data):
+        """Check if the data contains binary components."""
+        if isinstance(data, six.binary_type):
+            return True
+        elif isinstance(data, list):
+            return functools.reduce(
+                lambda a, b: a or b, [self._data_is_binary(item)
+                                      for item in data], False)
+        elif isinstance(data, dict):
+            return functools.reduce(
+                lambda a, b: a or b, [self._data_is_binary(item)
+                                      for item in six.itervalues(data)],
+                False)
+        else:
+            return False
diff --git a/libs/socketio/pubsub_manager.py b/libs/socketio/pubsub_manager.py
new file mode 100644
index 000000000..2905b2c32
--- /dev/null
+++ b/libs/socketio/pubsub_manager.py
@@ -0,0 +1,154 @@
+from functools import partial
+import uuid
+
+import json
+import pickle
+import six
+
+from .base_manager import BaseManager
+
+
+class PubSubManager(BaseManager):
+    """Manage a client list attached to a pub/sub backend.
+
+    This is a base class that enables multiple servers to share the list of
+    clients, with the servers communicating events through a pub/sub backend.
+    The use of a pub/sub backend also allows any client connected to the
+    backend to emit events addressed to Socket.IO clients.
+
+    The actual backends must be implemented by subclasses, this class only
+    provides a pub/sub generic framework.
+
+    :param channel: The channel name on which the server sends and receives
+                    notifications.
+    """
+    name = 'pubsub'
+
+    def __init__(self, channel='socketio', write_only=False, logger=None):
+        super(PubSubManager, self).__init__()
+        self.channel = channel
+        self.write_only = write_only
+        self.host_id = uuid.uuid4().hex
+        self.logger = logger
+
+    def initialize(self):
+        super(PubSubManager, self).initialize()
+        if not self.write_only:
+            self.thread = self.server.start_background_task(self._thread)
+        self._get_logger().info(self.name + ' backend initialized.')
+
+    def emit(self, event, data, namespace=None, room=None, skip_sid=None,
+             callback=None, **kwargs):
+        """Emit a message to a single client, a room, or all the clients
+        connected to the namespace.
+
+        This method takes care or propagating the message to all the servers
+        that are connected through the message queue.
+
+        The parameters are the same as in :meth:`.Server.emit`.
+        """
+        if kwargs.get('ignore_queue'):
+            return super(PubSubManager, self).emit(
+                event, data, namespace=namespace, room=room, skip_sid=skip_sid,
+                callback=callback)
+        namespace = namespace or '/'
+        if callback is not None:
+            if self.server is None:
+                raise RuntimeError('Callbacks can only be issued from the '
+                                   'context of a server.')
+            if room is None:
+                raise ValueError('Cannot use callback without a room set.')
+            id = self._generate_ack_id(room, namespace, callback)
+            callback = (room, namespace, id)
+        else:
+            callback = None
+        self._publish({'method': 'emit', 'event': event, 'data': data,
+                       'namespace': namespace, 'room': room,
+                       'skip_sid': skip_sid, 'callback': callback,
+                       'host_id': self.host_id})
+
+    def close_room(self, room, namespace=None):
+        self._publish({'method': 'close_room', 'room': room,
+                       'namespace': namespace or '/'})
+
+    def _publish(self, data):
+        """Publish a message on the Socket.IO channel.
+
+        This method needs to be implemented by the different subclasses that
+        support pub/sub backends.
+        """
+        raise NotImplementedError('This method must be implemented in a '
+                                  'subclass.')  # pragma: no cover
+
+    def _listen(self):
+        """Return the next message published on the Socket.IO channel,
+        blocking until a message is available.
+
+        This method needs to be implemented by the different subclasses that
+        support pub/sub backends.
+        """
+        raise NotImplementedError('This method must be implemented in a '
+                                  'subclass.')  # pragma: no cover
+
+    def _handle_emit(self, message):
+        # Events with callbacks are very tricky to handle across hosts
+        # Here in the receiving end we set up a local callback that preserves
+        # the callback host and id from the sender
+        remote_callback = message.get('callback')
+        remote_host_id = message.get('host_id')
+        if remote_callback is not None and len(remote_callback) == 3:
+            callback = partial(self._return_callback, remote_host_id,
+                               *remote_callback)
+        else:
+            callback = None
+        super(PubSubManager, self).emit(message['event'], message['data'],
+                                        namespace=message.get('namespace'),
+                                        room=message.get('room'),
+                                        skip_sid=message.get('skip_sid'),
+                                        callback=callback)
+
+    def _handle_callback(self, message):
+        if self.host_id == message.get('host_id'):
+            try:
+                sid = message['sid']
+                namespace = message['namespace']
+                id = message['id']
+                args = message['args']
+            except KeyError:
+                return
+            self.trigger_callback(sid, namespace, id, args)
+
+    def _return_callback(self, host_id, sid, namespace, callback_id, *args):
+        # When an event callback is received, the callback is returned back
+        # the sender, which is identified by the host_id
+        self._publish({'method': 'callback', 'host_id': host_id,
+                       'sid': sid, 'namespace': namespace, 'id': callback_id,
+                       'args': args})
+
+    def _handle_close_room(self, message):
+        super(PubSubManager, self).close_room(
+            room=message.get('room'), namespace=message.get('namespace'))
+
+    def _thread(self):
+        for message in self._listen():
+            data = None
+            if isinstance(message, dict):
+                data = message
+            else:
+                if isinstance(message, six.binary_type):  # pragma: no cover
+                    try:
+                        data = pickle.loads(message)
+                    except:
+                        pass
+                if data is None:
+                    try:
+                        data = json.loads(message)
+                    except:
+                        pass
+            if data and 'method' in data:
+                if data['method'] == 'emit':
+                    self._handle_emit(data)
+                elif data['method'] == 'callback':
+                    self._handle_callback(data)
+                elif data['method'] == 'close_room':
+                    self._handle_close_room(data)
diff --git a/libs/socketio/redis_manager.py b/libs/socketio/redis_manager.py
new file mode 100644
index 000000000..ad383345e
--- /dev/null
+++ b/libs/socketio/redis_manager.py
@@ -0,0 +1,115 @@
+import logging
+import pickle
+import time
+
+try:
+    import redis
+except ImportError:
+    redis = None
+
+from .pubsub_manager import PubSubManager
+
+logger = logging.getLogger('socketio')
+
+
+class RedisManager(PubSubManager):  # pragma: no cover
+    """Redis based client manager.
+
+    This class implements a Redis backend for event sharing across multiple
+    processes. Only kept here as one more example of how to build a custom
+    backend, since the kombu backend is perfectly adequate to support a Redis
+    message queue.
+
+    To use a Redis backend, initialize the :class:`Server` instance as
+    follows::
+
+        url = 'redis://hostname:port/0'
+        server = socketio.Server(client_manager=socketio.RedisManager(url))
+
+    :param url: The connection URL for the Redis server. For a default Redis
+                store running on the same host, use ``redis://``.
+    :param channel: The channel name on which the server sends and receives
+                    notifications. Must be the same in all the servers.
+    :param write_only: If set ot ``True``, only initialize to emit events. The
+                       default of ``False`` initializes the class for emitting
+                       and receiving.
+    :param redis_options: additional keyword arguments to be passed to
+                          ``Redis.from_url()``.
+    """
+    name = 'redis'
+
+    def __init__(self, url='redis://localhost:6379/0', channel='socketio',
+                 write_only=False, logger=None, redis_options=None):
+        if redis is None:
+            raise RuntimeError('Redis package is not installed '
+                               '(Run "pip install redis" in your '
+                               'virtualenv).')
+        self.redis_url = url
+        self.redis_options = redis_options or {}
+        self._redis_connect()
+        super(RedisManager, self).__init__(channel=channel,
+                                           write_only=write_only,
+                                           logger=logger)
+
+    def initialize(self):
+        super(RedisManager, self).initialize()
+
+        monkey_patched = True
+        if self.server.async_mode == 'eventlet':
+            from eventlet.patcher import is_monkey_patched
+            monkey_patched = is_monkey_patched('socket')
+        elif 'gevent' in self.server.async_mode:
+            from gevent.monkey import is_module_patched
+            monkey_patched = is_module_patched('socket')
+        if not monkey_patched:
+            raise RuntimeError(
+                'Redis requires a monkey patched socket library to work '
+                'with ' + self.server.async_mode)
+
+    def _redis_connect(self):
+        self.redis = redis.Redis.from_url(self.redis_url,
+                                          **self.redis_options)
+        self.pubsub = self.redis.pubsub()
+
+    def _publish(self, data):
+        retry = True
+        while True:
+            try:
+                if not retry:
+                    self._redis_connect()
+                return self.redis.publish(self.channel, pickle.dumps(data))
+            except redis.exceptions.ConnectionError:
+                if retry:
+                    logger.error('Cannot publish to redis... retrying')
+                    retry = False
+                else:
+                    logger.error('Cannot publish to redis... giving up')
+                    break
+
+    def _redis_listen_with_retries(self):
+        retry_sleep = 1
+        connect = False
+        while True:
+            try:
+                if connect:
+                    self._redis_connect()
+                    self.pubsub.subscribe(self.channel)
+                for message in self.pubsub.listen():
+                    yield message
+            except redis.exceptions.ConnectionError:
+                logger.error('Cannot receive from redis... '
+                             'retrying in {} secs'.format(retry_sleep))
+                connect = True
+                time.sleep(retry_sleep)
+                retry_sleep *= 2
+                if retry_sleep > 60:
+                    retry_sleep = 60
+
+    def _listen(self):
+        channel = self.channel.encode('utf-8')
+        self.pubsub.subscribe(self.channel)
+        for message in self._redis_listen_with_retries():
+            if message['channel'] == channel and \
+                    message['type'] == 'message' and 'data' in message:
+                yield message['data']
+        self.pubsub.unsubscribe(self.channel)
diff --git a/libs/socketio/server.py b/libs/socketio/server.py
new file mode 100644
index 000000000..76b7d2e8f
--- /dev/null
+++ b/libs/socketio/server.py
@@ -0,0 +1,730 @@
+import logging
+
+import engineio
+import six
+
+from . import base_manager
+from . import exceptions
+from . import namespace
+from . import packet
+
+default_logger = logging.getLogger('socketio.server')
+
+
+class Server(object):
+    """A Socket.IO server.
+
+    This class implements a fully compliant Socket.IO web server with support
+    for websocket and long-polling transports.
+
+    :param client_manager: The client manager instance that will manage the
+                           client list. When this is omitted, the client list
+                           is stored in an in-memory structure, so the use of
+                           multiple connected servers is not possible.
+    :param logger: To enable logging set to ``True`` or pass a logger object to
+                   use. To disable logging set to ``False``. The default is
+                   ``False``.
+    :param binary: ``True`` to support binary payloads, ``False`` to treat all
+                   payloads as text. On Python 2, if this is set to ``True``,
+                   ``unicode`` values are treated as text, and ``str`` and
+                   ``bytes`` values are treated as binary.  This option has no
+                   effect on Python 3, where text and binary payloads are
+                   always automatically discovered.
+    :param json: An alternative json module to use for encoding and decoding
+                 packets. Custom json modules must have ``dumps`` and ``loads``
+                 functions that are compatible with the standard library
+                 versions.
+    :param async_handlers: If set to ``True``, event handlers for a client are
+                           executed in separate threads. To run handlers for a
+                           client synchronously, set to ``False``. The default
+                           is ``True``.
+    :param always_connect: When set to ``False``, new connections are
+                           provisory until the connect handler returns
+                           something other than ``False``, at which point they
+                           are accepted. When set to ``True``, connections are
+                           immediately accepted, and then if the connect
+                           handler returns ``False`` a disconnect is issued.
+                           Set to ``True`` if you need to emit events from the
+                           connect handler and your client is confused when it
+                           receives events before the connection acceptance.
+                           In any other case use the default of ``False``.
+    :param kwargs: Connection parameters for the underlying Engine.IO server.
+
+    The Engine.IO configuration supports the following settings:
+
+    :param async_mode: The asynchronous model to use. See the Deployment
+                       section in the documentation for a description of the
+                       available options. Valid async modes are "threading",
+                       "eventlet", "gevent" and "gevent_uwsgi". If this
+                       argument is not given, "eventlet" is tried first, then
+                       "gevent_uwsgi", then "gevent", and finally "threading".
+                       The first async mode that has all its dependencies
+                       installed is then one that is chosen.
+    :param ping_timeout: The time in seconds that the client waits for the
+                         server to respond before disconnecting. The default
+                         is 60 seconds.
+    :param ping_interval: The interval in seconds at which the client pings
+                          the server. The default is 25 seconds.
+    :param max_http_buffer_size: The maximum size of a message when using the
+                                 polling transport. The default is 100,000,000
+                                 bytes.
+    :param allow_upgrades: Whether to allow transport upgrades or not. The
+                           default is ``True``.
+    :param http_compression: Whether to compress packages when using the
+                             polling transport. The default is ``True``.
+    :param compression_threshold: Only compress messages when their byte size
+                                  is greater than this value. The default is
+                                  1024 bytes.
+    :param cookie: Name of the HTTP cookie that contains the client session
+                   id. If set to ``None``, a cookie is not sent to the client.
+                   The default is ``'io'``.
+    :param cors_allowed_origins: Origin or list of origins that are allowed to
+                                 connect to this server. Only the same origin
+                                 is allowed by default. Set this argument to
+                                 ``'*'`` to allow all origins, or to ``[]`` to
+                                 disable CORS handling.
+    :param cors_credentials: Whether credentials (cookies, authentication) are
+                             allowed in requests to this server. The default is
+                             ``True``.
+    :param monitor_clients: If set to ``True``, a background task will ensure
+                            inactive clients are closed. Set to ``False`` to
+                            disable the monitoring task (not recommended). The
+                            default is ``True``.
+    :param engineio_logger: To enable Engine.IO logging set to ``True`` or pass
+                            a logger object to use. To disable logging set to
+                            ``False``. The default is ``False``.
+    """
+    def __init__(self, client_manager=None, logger=False, binary=False,
+                 json=None, async_handlers=True, always_connect=False,
+                 **kwargs):
+        engineio_options = kwargs
+        engineio_logger = engineio_options.pop('engineio_logger', None)
+        if engineio_logger is not None:
+            engineio_options['logger'] = engineio_logger
+        if json is not None:
+            packet.Packet.json = json
+            engineio_options['json'] = json
+        engineio_options['async_handlers'] = False
+        self.eio = self._engineio_server_class()(**engineio_options)
+        self.eio.on('connect', self._handle_eio_connect)
+        self.eio.on('message', self._handle_eio_message)
+        self.eio.on('disconnect', self._handle_eio_disconnect)
+        self.binary = binary
+
+        self.environ = {}
+        self.handlers = {}
+        self.namespace_handlers = {}
+
+        self._binary_packet = {}
+
+        if not isinstance(logger, bool):
+            self.logger = logger
+        else:
+            self.logger = default_logger
+            if not logging.root.handlers and \
+                    self.logger.level == logging.NOTSET:
+                if logger:
+                    self.logger.setLevel(logging.INFO)
+                else:
+                    self.logger.setLevel(logging.ERROR)
+                self.logger.addHandler(logging.StreamHandler())
+
+        if client_manager is None:
+            client_manager = base_manager.BaseManager()
+        self.manager = client_manager
+        self.manager.set_server(self)
+        self.manager_initialized = False
+
+        self.async_handlers = async_handlers
+        self.always_connect = always_connect
+
+        self.async_mode = self.eio.async_mode
+
+    def is_asyncio_based(self):
+        return False
+
+    def on(self, event, handler=None, namespace=None):
+        """Register an event handler.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param handler: The function that should be invoked to handle the
+                        event. When this parameter is not given, the method
+                        acts as a decorator for the handler function.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the handler is associated with
+                          the default namespace.
+
+        Example usage::
+
+            # as a decorator:
+            @socket_io.on('connect', namespace='/chat')
+            def connect_handler(sid, environ):
+                print('Connection request')
+                if environ['REMOTE_ADDR'] in blacklisted:
+                    return False  # reject
+
+            # as a method:
+            def message_handler(sid, msg):
+                print('Received message: ', msg)
+                eio.send(sid, 'response')
+            socket_io.on('message', namespace='/chat', message_handler)
+
+        The handler function receives the ``sid`` (session ID) for the
+        client as first argument. The ``'connect'`` event handler receives the
+        WSGI environment as a second argument, and can return ``False`` to
+        reject the connection. The ``'message'`` handler and handlers for
+        custom event names receive the message payload as a second argument.
+        Any values returned from a message handler will be passed to the
+        client's acknowledgement callback function if it exists. The
+        ``'disconnect'`` handler does not take a second argument.
+        """
+        namespace = namespace or '/'
+
+        def set_handler(handler):
+            if namespace not in self.handlers:
+                self.handlers[namespace] = {}
+            self.handlers[namespace][event] = handler
+            return handler
+
+        if handler is None:
+            return set_handler
+        set_handler(handler)
+
+    def event(self, *args, **kwargs):
+        """Decorator to register an event handler.
+
+        This is a simplified version of the ``on()`` method that takes the
+        event name from the decorated function.
+
+        Example usage::
+
+            @sio.event
+            def my_event(data):
+                print('Received data: ', data)
+
+        The above example is equivalent to::
+
+            @sio.on('my_event')
+            def my_event(data):
+                print('Received data: ', data)
+
+        A custom namespace can be given as an argument to the decorator::
+
+            @sio.event(namespace='/test')
+            def my_event(data):
+                print('Received data: ', data)
+        """
+        if len(args) == 1 and len(kwargs) == 0 and callable(args[0]):
+            # the decorator was invoked without arguments
+            # args[0] is the decorated function
+            return self.on(args[0].__name__)(args[0])
+        else:
+            # the decorator was invoked with arguments
+            def set_handler(handler):
+                return self.on(handler.__name__, *args, **kwargs)(handler)
+
+            return set_handler
+
+    def register_namespace(self, namespace_handler):
+        """Register a namespace handler object.
+
+        :param namespace_handler: An instance of a :class:`Namespace`
+                                  subclass that handles all the event traffic
+                                  for a namespace.
+        """
+        if not isinstance(namespace_handler, namespace.Namespace):
+            raise ValueError('Not a namespace instance')
+        if self.is_asyncio_based() != namespace_handler.is_asyncio_based():
+            raise ValueError('Not a valid namespace class for this server')
+        namespace_handler._set_server(self)
+        self.namespace_handlers[namespace_handler.namespace] = \
+            namespace_handler
+
+    def emit(self, event, data=None, to=None, room=None, skip_sid=None,
+             namespace=None, callback=None, **kwargs):
+        """Emit a custom event to one or more connected clients.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param to: The recipient of the message. This can be set to the
+                   session ID of a client to address only that client, or to
+                   to any custom room created by the application to address all
+                   the clients in that room, If this argument is omitted the
+                   event is broadcasted to all connected clients.
+        :param room: Alias for the ``to`` parameter.
+        :param skip_sid: The session ID of a client to skip when broadcasting
+                         to a room or to all clients. This can be used to
+                         prevent a message from being sent to the sender. To
+                         skip multiple sids, pass a list.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+        :param ignore_queue: Only used when a message queue is configured. If
+                             set to ``True``, the event is emitted to the
+                             clients directly, without going through the queue.
+                             This is more efficient, but only works when a
+                             single server process is used. It is recommended
+                             to always leave this parameter with its default
+                             value of ``False``.
+        """
+        namespace = namespace or '/'
+        room = to or room
+        self.logger.info('emitting event "%s" to %s [%s]', event,
+                         room or 'all', namespace)
+        self.manager.emit(event, data, namespace, room=room,
+                          skip_sid=skip_sid, callback=callback, **kwargs)
+
+    def send(self, data, to=None, room=None, skip_sid=None, namespace=None,
+             callback=None, **kwargs):
+        """Send a message to one or more connected clients.
+
+        This function emits an event with the name ``'message'``. Use
+        :func:`emit` to issue custom event names.
+
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param to: The recipient of the message. This can be set to the
+                   session ID of a client to address only that client, or to
+                   to any custom room created by the application to address all
+                   the clients in that room, If this argument is omitted the
+                   event is broadcasted to all connected clients.
+        :param room: Alias for the ``to`` parameter.
+        :param skip_sid: The session ID of a client to skip when broadcasting
+                         to a room or to all clients. This can be used to
+                         prevent a message from being sent to the sender. To
+                         skip multiple sids, pass a list.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param callback: If given, this function will be called to acknowledge
+                         the the client has received the message. The arguments
+                         that will be passed to the function are those provided
+                         by the client. Callback functions can only be used
+                         when addressing an individual client.
+        :param ignore_queue: Only used when a message queue is configured. If
+                             set to ``True``, the event is emitted to the
+                             clients directly, without going through the queue.
+                             This is more efficient, but only works when a
+                             single server process is used. It is recommended
+                             to always leave this parameter with its default
+                             value of ``False``.
+        """
+        self.emit('message', data=data, to=to, room=room, skip_sid=skip_sid,
+                  namespace=namespace, callback=callback, **kwargs)
+
+    def call(self, event, data=None, to=None, sid=None, namespace=None,
+             timeout=60, **kwargs):
+        """Emit a custom event to a client and wait for the response.
+
+        :param event: The event name. It can be any string. The event names
+                      ``'connect'``, ``'message'`` and ``'disconnect'`` are
+                      reserved and should not be used.
+        :param data: The data to send to the client or clients. Data can be of
+                     type ``str``, ``bytes``, ``list`` or ``dict``. If a
+                     ``list`` or ``dict``, the data will be serialized as JSON.
+        :param to: The session ID of the recipient client.
+        :param sid: Alias for the ``to`` parameter.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the event is emitted to the
+                          default namespace.
+        :param timeout: The waiting timeout. If the timeout is reached before
+                        the client acknowledges the event, then a
+                        ``TimeoutError`` exception is raised.
+        :param ignore_queue: Only used when a message queue is configured. If
+                             set to ``True``, the event is emitted to the
+                             client directly, without going through the queue.
+                             This is more efficient, but only works when a
+                             single server process is used. It is recommended
+                             to always leave this parameter with its default
+                             value of ``False``.
+        """
+        if not self.async_handlers:
+            raise RuntimeError(
+                'Cannot use call() when async_handlers is False.')
+        callback_event = self.eio.create_event()
+        callback_args = []
+
+        def event_callback(*args):
+            callback_args.append(args)
+            callback_event.set()
+
+        self.emit(event, data=data, room=to or sid, namespace=namespace,
+                  callback=event_callback, **kwargs)
+        if not callback_event.wait(timeout=timeout):
+            raise exceptions.TimeoutError()
+        return callback_args[0] if len(callback_args[0]) > 1 \
+            else callback_args[0][0] if len(callback_args[0]) == 1 \
+            else None
+
+    def enter_room(self, sid, room, namespace=None):
+        """Enter a room.
+
+        This function adds the client to a room. The :func:`emit` and
+        :func:`send` functions can optionally broadcast events to all the
+        clients in a room.
+
+        :param sid: Session ID of the client.
+        :param room: Room name. If the room does not exist it is created.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the default namespace is used.
+        """
+        namespace = namespace or '/'
+        self.logger.info('%s is entering room %s [%s]', sid, room, namespace)
+        self.manager.enter_room(sid, namespace, room)
+
+    def leave_room(self, sid, room, namespace=None):
+        """Leave a room.
+
+        This function removes the client from a room.
+
+        :param sid: Session ID of the client.
+        :param room: Room name.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the default namespace is used.
+        """
+        namespace = namespace or '/'
+        self.logger.info('%s is leaving room %s [%s]', sid, room, namespace)
+        self.manager.leave_room(sid, namespace, room)
+
+    def close_room(self, room, namespace=None):
+        """Close a room.
+
+        This function removes all the clients from the given room.
+
+        :param room: Room name.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the default namespace is used.
+        """
+        namespace = namespace or '/'
+        self.logger.info('room %s is closing [%s]', room, namespace)
+        self.manager.close_room(room, namespace)
+
+    def rooms(self, sid, namespace=None):
+        """Return the rooms a client is in.
+
+        :param sid: Session ID of the client.
+        :param namespace: The Socket.IO namespace for the event. If this
+                          argument is omitted the default namespace is used.
+        """
+        namespace = namespace or '/'
+        return self.manager.get_rooms(sid, namespace)
+
+    def get_session(self, sid, namespace=None):
+        """Return the user session for a client.
+
+        :param sid: The session id of the client.
+        :param namespace: The Socket.IO namespace. If this argument is omitted
+                          the default namespace is used.
+
+        The return value is a dictionary. Modifications made to this
+        dictionary are not guaranteed to be preserved unless
+        ``save_session()`` is called, or when the ``session`` context manager
+        is used.
+        """
+        namespace = namespace or '/'
+        eio_session = self.eio.get_session(sid)
+        return eio_session.setdefault(namespace, {})
+
+    def save_session(self, sid, session, namespace=None):
+        """Store the user session for a client.
+
+        :param sid: The session id of the client.
+        :param session: The session dictionary.
+        :param namespace: The Socket.IO namespace. If this argument is omitted
+                          the default namespace is used.
+        """
+        namespace = namespace or '/'
+        eio_session = self.eio.get_session(sid)
+        eio_session[namespace] = session
+
+    def session(self, sid, namespace=None):
+        """Return the user session for a client with context manager syntax.
+
+        :param sid: The session id of the client.
+
+        This is a context manager that returns the user session dictionary for
+        the client. Any changes that are made to this dictionary inside the
+        context manager block are saved back to the session. Example usage::
+
+            @sio.on('connect')
+            def on_connect(sid, environ):
+                username = authenticate_user(environ)
+                if not username:
+                    return False
+                with sio.session(sid) as session:
+                    session['username'] = username
+
+            @sio.on('message')
+            def on_message(sid, msg):
+                with sio.session(sid) as session:
+                    print('received message from ', session['username'])
+        """
+        class _session_context_manager(object):
+            def __init__(self, server, sid, namespace):
+                self.server = server
+                self.sid = sid
+                self.namespace = namespace
+                self.session = None
+
+            def __enter__(self):
+                self.session = self.server.get_session(sid,
+                                                       namespace=namespace)
+                return self.session
+
+            def __exit__(self, *args):
+                self.server.save_session(sid, self.session,
+                                         namespace=namespace)
+
+        return _session_context_manager(self, sid, namespace)
+
+    def disconnect(self, sid, namespace=None):
+        """Disconnect a client.
+
+        :param sid: Session ID of the client.
+        :param namespace: The Socket.IO namespace to disconnect. If this
+                          argument is omitted the default namespace is used.
+        """
+        namespace = namespace or '/'
+        if self.manager.is_connected(sid, namespace=namespace):
+            self.logger.info('Disconnecting %s [%s]', sid, namespace)
+            self.manager.pre_disconnect(sid, namespace=namespace)
+            self._send_packet(sid, packet.Packet(packet.DISCONNECT,
+                                                 namespace=namespace))
+            self._trigger_event('disconnect', namespace, sid)
+            self.manager.disconnect(sid, namespace=namespace)
+            if namespace == '/':
+                self.eio.disconnect(sid)
+
+    def transport(self, sid):
+        """Return the name of the transport used by the client.
+
+        The two possible values returned by this function are ``'polling'``
+        and ``'websocket'``.
+
+        :param sid: The session of the client.
+        """
+        return self.eio.transport(sid)
+
+    def handle_request(self, environ, start_response):
+        """Handle an HTTP request from the client.
+
+        This is the entry point of the Socket.IO application, using the same
+        interface as a WSGI application. For the typical usage, this function
+        is invoked by the :class:`Middleware` instance, but it can be invoked
+        directly when the middleware is not used.
+
+        :param environ: The WSGI environment.
+        :param start_response: The WSGI ``start_response`` function.
+
+        This function returns the HTTP response body to deliver to the client
+        as a byte sequence.
+        """
+        return self.eio.handle_request(environ, start_response)
+
+    def start_background_task(self, target, *args, **kwargs):
+        """Start a background task using the appropriate async model.
+
+        This is a utility function that applications can use to start a
+        background task using the method that is compatible with the
+        selected async mode.
+
+        :param target: the target function to execute.
+        :param args: arguments to pass to the function.
+        :param kwargs: keyword arguments to pass to the function.
+
+        This function returns an object compatible with the `Thread` class in
+        the Python standard library. The `start()` method on this object is
+        already called by this function.
+        """
+        return self.eio.start_background_task(target, *args, **kwargs)
+
+    def sleep(self, seconds=0):
+        """Sleep for the requested amount of time using the appropriate async
+        model.
+
+        This is a utility function that applications can use to put a task to
+        sleep without having to worry about using the correct call for the
+        selected async mode.
+        """
+        return self.eio.sleep(seconds)
+
+    def _emit_internal(self, sid, event, data, namespace=None, id=None):
+        """Send a message to a client."""
+        if six.PY2 and not self.binary:
+            binary = False  # pragma: nocover
+        else:
+            binary = None
+        # tuples are expanded to multiple arguments, everything else is sent
+        # as a single argument
+        if isinstance(data, tuple):
+            data = list(data)
+        else:
+            data = [data]
+        self._send_packet(sid, packet.Packet(packet.EVENT, namespace=namespace,
+                                             data=[event] + data, id=id,
+                                             binary=binary))
+
+    def _send_packet(self, sid, pkt):
+        """Send a Socket.IO packet to a client."""
+        encoded_packet = pkt.encode()
+        if isinstance(encoded_packet, list):
+            binary = False
+            for ep in encoded_packet:
+                self.eio.send(sid, ep, binary=binary)
+                binary = True
+        else:
+            self.eio.send(sid, encoded_packet, binary=False)
+
+    def _handle_connect(self, sid, namespace):
+        """Handle a client connection request."""
+        namespace = namespace or '/'
+        self.manager.connect(sid, namespace)
+        if self.always_connect:
+            self._send_packet(sid, packet.Packet(packet.CONNECT,
+                                                 namespace=namespace))
+        fail_reason = None
+        try:
+            success = self._trigger_event('connect', namespace, sid,
+                                          self.environ[sid])
+        except exceptions.ConnectionRefusedError as exc:
+            fail_reason = exc.error_args
+            success = False
+
+        if success is False:
+            if self.always_connect:
+                self.manager.pre_disconnect(sid, namespace)
+                self._send_packet(sid, packet.Packet(
+                    packet.DISCONNECT, data=fail_reason, namespace=namespace))
+            self.manager.disconnect(sid, namespace)
+            if not self.always_connect:
+                self._send_packet(sid, packet.Packet(
+                    packet.ERROR, data=fail_reason, namespace=namespace))
+            if sid in self.environ:  # pragma: no cover
+                del self.environ[sid]
+        elif not self.always_connect:
+            self._send_packet(sid, packet.Packet(packet.CONNECT,
+                                                 namespace=namespace))
+
+    def _handle_disconnect(self, sid, namespace):
+        """Handle a client disconnect."""
+        namespace = namespace or '/'
+        if namespace == '/':
+            namespace_list = list(self.manager.get_namespaces())
+        else:
+            namespace_list = [namespace]
+        for n in namespace_list:
+            if n != '/' and self.manager.is_connected(sid, n):
+                self._trigger_event('disconnect', n, sid)
+                self.manager.disconnect(sid, n)
+        if namespace == '/' and self.manager.is_connected(sid, namespace):
+            self._trigger_event('disconnect', '/', sid)
+            self.manager.disconnect(sid, '/')
+
+    def _handle_event(self, sid, namespace, id, data):
+        """Handle an incoming client event."""
+        namespace = namespace or '/'
+        self.logger.info('received event "%s" from %s [%s]', data[0], sid,
+                         namespace)
+        if not self.manager.is_connected(sid, namespace):
+            self.logger.warning('%s is not connected to namespace %s',
+                                sid, namespace)
+            return
+        if self.async_handlers:
+            self.start_background_task(self._handle_event_internal, self, sid,
+                                       data, namespace, id)
+        else:
+            self._handle_event_internal(self, sid, data, namespace, id)
+
+    def _handle_event_internal(self, server, sid, data, namespace, id):
+        r = server._trigger_event(data[0], namespace, sid, *data[1:])
+        if id is not None:
+            # send ACK packet with the response returned by the handler
+            # tuples are expanded as multiple arguments
+            if r is None:
+                data = []
+            elif isinstance(r, tuple):
+                data = list(r)
+            else:
+                data = [r]
+            if six.PY2 and not self.binary:
+                binary = False  # pragma: nocover
+            else:
+                binary = None
+            server._send_packet(sid, packet.Packet(packet.ACK,
+                                                   namespace=namespace,
+                                                   id=id, data=data,
+                                                   binary=binary))
+
+    def _handle_ack(self, sid, namespace, id, data):
+        """Handle ACK packets from the client."""
+        namespace = namespace or '/'
+        self.logger.info('received ack from %s [%s]', sid, namespace)
+        self.manager.trigger_callback(sid, namespace, id, data)
+
+    def _trigger_event(self, event, namespace, *args):
+        """Invoke an application event handler."""
+        # first see if we have an explicit handler for the event
+        if namespace in self.handlers and event in self.handlers[namespace]:
+            return self.handlers[namespace][event](*args)
+
+        # or else, forward the event to a namespace handler if one exists
+        elif namespace in self.namespace_handlers:
+            return self.namespace_handlers[namespace].trigger_event(
+                event, *args)
+
+    def _handle_eio_connect(self, sid, environ):
+        """Handle the Engine.IO connection event."""
+        if not self.manager_initialized:
+            self.manager_initialized = True
+            self.manager.initialize()
+        self.environ[sid] = environ
+        return self._handle_connect(sid, '/')
+
+    def _handle_eio_message(self, sid, data):
+        """Dispatch Engine.IO messages."""
+        if sid in self._binary_packet:
+            pkt = self._binary_packet[sid]
+            if pkt.add_attachment(data):
+                del self._binary_packet[sid]
+                if pkt.packet_type == packet.BINARY_EVENT:
+                    self._handle_event(sid, pkt.namespace, pkt.id, pkt.data)
+                else:
+                    self._handle_ack(sid, pkt.namespace, pkt.id, pkt.data)
+        else:
+            pkt = packet.Packet(encoded_packet=data)
+            if pkt.packet_type == packet.CONNECT:
+                self._handle_connect(sid, pkt.namespace)
+            elif pkt.packet_type == packet.DISCONNECT:
+                self._handle_disconnect(sid, pkt.namespace)
+            elif pkt.packet_type == packet.EVENT:
+                self._handle_event(sid, pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.ACK:
+                self._handle_ack(sid, pkt.namespace, pkt.id, pkt.data)
+            elif pkt.packet_type == packet.BINARY_EVENT or \
+                    pkt.packet_type == packet.BINARY_ACK:
+                self._binary_packet[sid] = pkt
+            elif pkt.packet_type == packet.ERROR:
+                raise ValueError('Unexpected ERROR packet.')
+            else:
+                raise ValueError('Unknown packet type.')
+
+    def _handle_eio_disconnect(self, sid):
+        """Handle Engine.IO disconnect event."""
+        self._handle_disconnect(sid, '/')
+        if sid in self.environ:
+            del self.environ[sid]
+
+    def _engineio_server_class(self):
+        return engineio.Server
diff --git a/libs/socketio/tornado.py b/libs/socketio/tornado.py
new file mode 100644
index 000000000..5b2e6f684
--- /dev/null
+++ b/libs/socketio/tornado.py
@@ -0,0 +1,11 @@
+import sys
+if sys.version_info >= (3, 5):
+    try:
+        from engineio.async_drivers.tornado import get_tornado_handler as \
+            get_engineio_handler
+    except ImportError:  # pragma: no cover
+        get_engineio_handler = None
+
+
+def get_tornado_handler(socketio_server):  # pragma: no cover
+    return get_engineio_handler(socketio_server.eio)
diff --git a/libs/socketio/zmq_manager.py b/libs/socketio/zmq_manager.py
new file mode 100644
index 000000000..f2a2ae5dc
--- /dev/null
+++ b/libs/socketio/zmq_manager.py
@@ -0,0 +1,111 @@
+import pickle
+import re
+
+try:
+    import eventlet.green.zmq as zmq
+except ImportError:
+    zmq = None
+import six
+
+from .pubsub_manager import PubSubManager
+
+
+class ZmqManager(PubSubManager):  # pragma: no cover
+    """zmq based client manager.
+
+    NOTE: this zmq implementation should be considered experimental at this
+    time. At this time, eventlet is required to use zmq.
+
+    This class implements a zmq backend for event sharing across multiple
+    processes. To use a zmq backend, initialize the :class:`Server` instance as
+    follows::
+
+        url = 'zmq+tcp://hostname:port1+port2'
+        server = socketio.Server(client_manager=socketio.ZmqManager(url))
+
+    :param url: The connection URL for the zmq message broker,
+                which will need to be provided and running.
+    :param channel: The channel name on which the server sends and receives
+                    notifications. Must be the same in all the servers.
+    :param write_only: If set to ``True``, only initialize to emit events. The
+                       default of ``False`` initializes the class for emitting
+                       and receiving.
+
+    A zmq message broker must be running for the zmq_manager to work.
+    you can write your own or adapt one from the following simple broker
+    below::
+
+        import zmq
+
+        receiver = zmq.Context().socket(zmq.PULL)
+        receiver.bind("tcp://*:5555")
+
+        publisher = zmq.Context().socket(zmq.PUB)
+        publisher.bind("tcp://*:5556")
+
+        while True:
+            publisher.send(receiver.recv())
+    """
+    name = 'zmq'
+
+    def __init__(self, url='zmq+tcp://localhost:5555+5556',
+                 channel='socketio',
+                 write_only=False,
+                 logger=None):
+        if zmq is None:
+            raise RuntimeError('zmq package is not installed '
+                               '(Run "pip install pyzmq" in your '
+                               'virtualenv).')
+
+        r = re.compile(r':\d+\+\d+$')
+        if not (url.startswith('zmq+tcp://') and r.search(url)):
+            raise RuntimeError('unexpected connection string: ' + url)
+
+        url = url.replace('zmq+', '')
+        (sink_url, sub_port) = url.split('+')
+        sink_port = sink_url.split(':')[-1]
+        sub_url = sink_url.replace(sink_port, sub_port)
+
+        sink = zmq.Context().socket(zmq.PUSH)
+        sink.connect(sink_url)
+
+        sub = zmq.Context().socket(zmq.SUB)
+        sub.setsockopt_string(zmq.SUBSCRIBE, u'')
+        sub.connect(sub_url)
+
+        self.sink = sink
+        self.sub = sub
+        self.channel = channel
+        super(ZmqManager, self).__init__(channel=channel,
+                                         write_only=write_only,
+                                         logger=logger)
+
+    def _publish(self, data):
+        pickled_data = pickle.dumps(
+            {
+                'type': 'message',
+                'channel': self.channel,
+                'data': data
+            }
+        )
+        return self.sink.send(pickled_data)
+
+    def zmq_listen(self):
+        while True:
+            response = self.sub.recv()
+            if response is not None:
+                yield response
+
+    def _listen(self):
+        for message in self.zmq_listen():
+            if isinstance(message, six.binary_type):
+                try:
+                    message = pickle.loads(message)
+                except Exception:
+                    pass
+            if isinstance(message, dict) and \
+                    message['type'] == 'message' and \
+                    message['channel'] == self.channel and \
+                    'data' in message:
+                yield message['data']
+        return
diff --git a/libs/yaml/__init__.py b/libs/yaml/__init__.py
new file mode 100644
index 000000000..5df0bb5fd
--- /dev/null
+++ b/libs/yaml/__init__.py
@@ -0,0 +1,402 @@
+
+from .error import *
+
+from .tokens import *
+from .events import *
+from .nodes import *
+
+from .loader import *
+from .dumper import *
+
+__version__ = '5.1'
+try:
+    from .cyaml import *
+    __with_libyaml__ = True
+except ImportError:
+    __with_libyaml__ = False
+
+import io
+
+#------------------------------------------------------------------------------
+# Warnings control
+#------------------------------------------------------------------------------
+
+# 'Global' warnings state:
+_warnings_enabled = {
+    'YAMLLoadWarning': True,
+}
+
+# Get or set global warnings' state
+def warnings(settings=None):
+    if settings is None:
+        return _warnings_enabled
+
+    if type(settings) is dict:
+        for key in settings:
+            if key in _warnings_enabled:
+                _warnings_enabled[key] = settings[key]
+
+# Warn when load() is called without Loader=...
+class YAMLLoadWarning(RuntimeWarning):
+    pass
+
+def load_warning(method):
+    if _warnings_enabled['YAMLLoadWarning'] is False:
+        return
+
+    import warnings
+
+    message = (
+        "calling yaml.%s() without Loader=... is deprecated, as the "
+        "default Loader is unsafe. Please read "
+        "https://msg.pyyaml.org/load for full details."
+    ) % method
+
+    warnings.warn(message, YAMLLoadWarning, stacklevel=3)
+
+#------------------------------------------------------------------------------
+def scan(stream, Loader=Loader):
+    """
+    Scan a YAML stream and produce scanning tokens.
+    """
+    loader = Loader(stream)
+    try:
+        while loader.check_token():
+            yield loader.get_token()
+    finally:
+        loader.dispose()
+
+def parse(stream, Loader=Loader):
+    """
+    Parse a YAML stream and produce parsing events.
+    """
+    loader = Loader(stream)
+    try:
+        while loader.check_event():
+            yield loader.get_event()
+    finally:
+        loader.dispose()
+
+def compose(stream, Loader=Loader):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding representation tree.
+    """
+    loader = Loader(stream)
+    try:
+        return loader.get_single_node()
+    finally:
+        loader.dispose()
+
+def compose_all(stream, Loader=Loader):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding representation trees.
+    """
+    loader = Loader(stream)
+    try:
+        while loader.check_node():
+            yield loader.get_node()
+    finally:
+        loader.dispose()
+
+def load(stream, Loader=None):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding Python object.
+    """
+    if Loader is None:
+        load_warning('load')
+        Loader = FullLoader
+
+    loader = Loader(stream)
+    try:
+        return loader.get_single_data()
+    finally:
+        loader.dispose()
+
+def load_all(stream, Loader=None):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding Python objects.
+    """
+    if Loader is None:
+        load_warning('load_all')
+        Loader = FullLoader
+
+    loader = Loader(stream)
+    try:
+        while loader.check_data():
+            yield loader.get_data()
+    finally:
+        loader.dispose()
+
+def full_load(stream):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding Python object.
+
+    Resolve all tags except those known to be
+    unsafe on untrusted input.
+    """
+    return load(stream, FullLoader)
+
+def full_load_all(stream):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding Python objects.
+
+    Resolve all tags except those known to be
+    unsafe on untrusted input.
+    """
+    return load_all(stream, FullLoader)
+
+def safe_load(stream):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding Python object.
+
+    Resolve only basic YAML tags. This is known
+    to be safe for untrusted input.
+    """
+    return load(stream, SafeLoader)
+
+def safe_load_all(stream):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding Python objects.
+
+    Resolve only basic YAML tags. This is known
+    to be safe for untrusted input.
+    """
+    return load_all(stream, SafeLoader)
+
+def unsafe_load(stream):
+    """
+    Parse the first YAML document in a stream
+    and produce the corresponding Python object.
+
+    Resolve all tags, even those known to be
+    unsafe on untrusted input.
+    """
+    return load(stream, UnsafeLoader)
+
+def unsafe_load_all(stream):
+    """
+    Parse all YAML documents in a stream
+    and produce corresponding Python objects.
+
+    Resolve all tags, even those known to be
+    unsafe on untrusted input.
+    """
+    return load_all(stream, UnsafeLoader)
+
+def emit(events, stream=None, Dumper=Dumper,
+        canonical=None, indent=None, width=None,
+        allow_unicode=None, line_break=None):
+    """
+    Emit YAML parsing events into a stream.
+    If stream is None, return the produced string instead.
+    """
+    getvalue = None
+    if stream is None:
+        stream = io.StringIO()
+        getvalue = stream.getvalue
+    dumper = Dumper(stream, canonical=canonical, indent=indent, width=width,
+            allow_unicode=allow_unicode, line_break=line_break)
+    try:
+        for event in events:
+            dumper.emit(event)
+    finally:
+        dumper.dispose()
+    if getvalue:
+        return getvalue()
+
+def serialize_all(nodes, stream=None, Dumper=Dumper,
+        canonical=None, indent=None, width=None,
+        allow_unicode=None, line_break=None,
+        encoding=None, explicit_start=None, explicit_end=None,
+        version=None, tags=None):
+    """
+    Serialize a sequence of representation trees into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    getvalue = None
+    if stream is None:
+        if encoding is None:
+            stream = io.StringIO()
+        else:
+            stream = io.BytesIO()
+        getvalue = stream.getvalue
+    dumper = Dumper(stream, canonical=canonical, indent=indent, width=width,
+            allow_unicode=allow_unicode, line_break=line_break,
+            encoding=encoding, version=version, tags=tags,
+            explicit_start=explicit_start, explicit_end=explicit_end)
+    try:
+        dumper.open()
+        for node in nodes:
+            dumper.serialize(node)
+        dumper.close()
+    finally:
+        dumper.dispose()
+    if getvalue:
+        return getvalue()
+
+def serialize(node, stream=None, Dumper=Dumper, **kwds):
+    """
+    Serialize a representation tree into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    return serialize_all([node], stream, Dumper=Dumper, **kwds)
+
+def dump_all(documents, stream=None, Dumper=Dumper,
+        default_style=None, default_flow_style=False,
+        canonical=None, indent=None, width=None,
+        allow_unicode=None, line_break=None,
+        encoding=None, explicit_start=None, explicit_end=None,
+        version=None, tags=None, sort_keys=True):
+    """
+    Serialize a sequence of Python objects into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    getvalue = None
+    if stream is None:
+        if encoding is None:
+            stream = io.StringIO()
+        else:
+            stream = io.BytesIO()
+        getvalue = stream.getvalue
+    dumper = Dumper(stream, default_style=default_style,
+            default_flow_style=default_flow_style,
+            canonical=canonical, indent=indent, width=width,
+            allow_unicode=allow_unicode, line_break=line_break,
+            encoding=encoding, version=version, tags=tags,
+            explicit_start=explicit_start, explicit_end=explicit_end, sort_keys=sort_keys)
+    try:
+        dumper.open()
+        for data in documents:
+            dumper.represent(data)
+        dumper.close()
+    finally:
+        dumper.dispose()
+    if getvalue:
+        return getvalue()
+
+def dump(data, stream=None, Dumper=Dumper, **kwds):
+    """
+    Serialize a Python object into a YAML stream.
+    If stream is None, return the produced string instead.
+    """
+    return dump_all([data], stream, Dumper=Dumper, **kwds)
+
+def safe_dump_all(documents, stream=None, **kwds):
+    """
+    Serialize a sequence of Python objects into a YAML stream.
+    Produce only basic YAML tags.
+    If stream is None, return the produced string instead.
+    """
+    return dump_all(documents, stream, Dumper=SafeDumper, **kwds)
+
+def safe_dump(data, stream=None, **kwds):
+    """
+    Serialize a Python object into a YAML stream.
+    Produce only basic YAML tags.
+    If stream is None, return the produced string instead.
+    """
+    return dump_all([data], stream, Dumper=SafeDumper, **kwds)
+
+def add_implicit_resolver(tag, regexp, first=None,
+        Loader=Loader, Dumper=Dumper):
+    """
+    Add an implicit scalar detector.
+    If an implicit scalar value matches the given regexp,
+    the corresponding tag is assigned to the scalar.
+    first is a sequence of possible initial characters or None.
+    """
+    Loader.add_implicit_resolver(tag, regexp, first)
+    Dumper.add_implicit_resolver(tag, regexp, first)
+
+def add_path_resolver(tag, path, kind=None, Loader=Loader, Dumper=Dumper):
+    """
+    Add a path based resolver for the given tag.
+    A path is a list of keys that forms a path
+    to a node in the representation tree.
+    Keys can be string values, integers, or None.
+    """
+    Loader.add_path_resolver(tag, path, kind)
+    Dumper.add_path_resolver(tag, path, kind)
+
+def add_constructor(tag, constructor, Loader=Loader):
+    """
+    Add a constructor for the given tag.
+    Constructor is a function that accepts a Loader instance
+    and a node object and produces the corresponding Python object.
+    """
+    Loader.add_constructor(tag, constructor)
+
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+    """
+    Add a multi-constructor for the given tag prefix.
+    Multi-constructor is called for a node if its tag starts with tag_prefix.
+    Multi-constructor accepts a Loader instance, a tag suffix,
+    and a node object and produces the corresponding Python object.
+    """
+    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+
+def add_representer(data_type, representer, Dumper=Dumper):
+    """
+    Add a representer for the given type.
+    Representer is a function accepting a Dumper instance
+    and an instance of the given data type
+    and producing the corresponding representation node.
+    """
+    Dumper.add_representer(data_type, representer)
+
+def add_multi_representer(data_type, multi_representer, Dumper=Dumper):
+    """
+    Add a representer for the given type.
+    Multi-representer is a function accepting a Dumper instance
+    and an instance of the given data type or subtype
+    and producing the corresponding representation node.
+    """
+    Dumper.add_multi_representer(data_type, multi_representer)
+
+class YAMLObjectMetaclass(type):
+    """
+    The metaclass for YAMLObject.
+    """
+    def __init__(cls, name, bases, kwds):
+        super(YAMLObjectMetaclass, cls).__init__(name, bases, kwds)
+        if 'yaml_tag' in kwds and kwds['yaml_tag'] is not None:
+            cls.yaml_loader.add_constructor(cls.yaml_tag, cls.from_yaml)
+            cls.yaml_dumper.add_representer(cls, cls.to_yaml)
+
+class YAMLObject(metaclass=YAMLObjectMetaclass):
+    """
+    An object that can dump itself to a YAML stream
+    and load itself from a YAML stream.
+    """
+
+    __slots__ = ()  # no direct instantiation, so allow immutable subclasses
+
+    yaml_loader = Loader
+    yaml_dumper = Dumper
+
+    yaml_tag = None
+    yaml_flow_style = None
+
+    @classmethod
+    def from_yaml(cls, loader, node):
+        """
+        Convert a representation node to a Python object.
+        """
+        return loader.construct_yaml_object(node, cls)
+
+    @classmethod
+    def to_yaml(cls, dumper, data):
+        """
+        Convert a Python object to a representation node.
+        """
+        return dumper.represent_yaml_object(cls.yaml_tag, data, cls,
+                flow_style=cls.yaml_flow_style)
+
diff --git a/libs/yaml/composer.py b/libs/yaml/composer.py
new file mode 100644
index 000000000..6d15cb40e
--- /dev/null
+++ b/libs/yaml/composer.py
@@ -0,0 +1,139 @@
+
+__all__ = ['Composer', 'ComposerError']
+
+from .error import MarkedYAMLError
+from .events import *
+from .nodes import *
+
+class ComposerError(MarkedYAMLError):
+    pass
+
+class Composer:
+
+    def __init__(self):
+        self.anchors = {}
+
+    def check_node(self):
+        # Drop the STREAM-START event.
+        if self.check_event(StreamStartEvent):
+            self.get_event()
+
+        # If there are more documents available?
+        return not self.check_event(StreamEndEvent)
+
+    def get_node(self):
+        # Get the root node of the next document.
+        if not self.check_event(StreamEndEvent):
+            return self.compose_document()
+
+    def get_single_node(self):
+        # Drop the STREAM-START event.
+        self.get_event()
+
+        # Compose a document if the stream is not empty.
+        document = None
+        if not self.check_event(StreamEndEvent):
+            document = self.compose_document()
+
+        # Ensure that the stream contains no more documents.
+        if not self.check_event(StreamEndEvent):
+            event = self.get_event()
+            raise ComposerError("expected a single document in the stream",
+                    document.start_mark, "but found another document",
+                    event.start_mark)
+
+        # Drop the STREAM-END event.
+        self.get_event()
+
+        return document
+
+    def compose_document(self):
+        # Drop the DOCUMENT-START event.
+        self.get_event()
+
+        # Compose the root node.
+        node = self.compose_node(None, None)
+
+        # Drop the DOCUMENT-END event.
+        self.get_event()
+
+        self.anchors = {}
+        return node
+
+    def compose_node(self, parent, index):
+        if self.check_event(AliasEvent):
+            event = self.get_event()
+            anchor = event.anchor
+            if anchor not in self.anchors:
+                raise ComposerError(None, None, "found undefined alias %r"
+                        % anchor, event.start_mark)
+            return self.anchors[anchor]
+        event = self.peek_event()
+        anchor = event.anchor
+        if anchor is not None:
+            if anchor in self.anchors:
+                raise ComposerError("found duplicate anchor %r; first occurrence"
+                        % anchor, self.anchors[anchor].start_mark,
+                        "second occurrence", event.start_mark)
+        self.descend_resolver(parent, index)
+        if self.check_event(ScalarEvent):
+            node = self.compose_scalar_node(anchor)
+        elif self.check_event(SequenceStartEvent):
+            node = self.compose_sequence_node(anchor)
+        elif self.check_event(MappingStartEvent):
+            node = self.compose_mapping_node(anchor)
+        self.ascend_resolver()
+        return node
+
+    def compose_scalar_node(self, anchor):
+        event = self.get_event()
+        tag = event.tag
+        if tag is None or tag == '!':
+            tag = self.resolve(ScalarNode, event.value, event.implicit)
+        node = ScalarNode(tag, event.value,
+                event.start_mark, event.end_mark, style=event.style)
+        if anchor is not None:
+            self.anchors[anchor] = node
+        return node
+
+    def compose_sequence_node(self, anchor):
+        start_event = self.get_event()
+        tag = start_event.tag
+        if tag is None or tag == '!':
+            tag = self.resolve(SequenceNode, None, start_event.implicit)
+        node = SequenceNode(tag, [],
+                start_event.start_mark, None,
+                flow_style=start_event.flow_style)
+        if anchor is not None:
+            self.anchors[anchor] = node
+        index = 0
+        while not self.check_event(SequenceEndEvent):
+            node.value.append(self.compose_node(node, index))
+            index += 1
+        end_event = self.get_event()
+        node.end_mark = end_event.end_mark
+        return node
+
+    def compose_mapping_node(self, anchor):
+        start_event = self.get_event()
+        tag = start_event.tag
+        if tag is None or tag == '!':
+            tag = self.resolve(MappingNode, None, start_event.implicit)
+        node = MappingNode(tag, [],
+                start_event.start_mark, None,
+                flow_style=start_event.flow_style)
+        if anchor is not None:
+            self.anchors[anchor] = node
+        while not self.check_event(MappingEndEvent):
+            #key_event = self.peek_event()
+            item_key = self.compose_node(node, None)
+            #if item_key in node.value:
+            #    raise ComposerError("while composing a mapping", start_event.start_mark,
+            #            "found duplicate key", key_event.start_mark)
+            item_value = self.compose_node(node, item_key)
+            #node.value[item_key] = item_value
+            node.value.append((item_key, item_value))
+        end_event = self.get_event()
+        node.end_mark = end_event.end_mark
+        return node
+
diff --git a/libs/yaml/constructor.py b/libs/yaml/constructor.py
new file mode 100644
index 000000000..34fc1ae92
--- /dev/null
+++ b/libs/yaml/constructor.py
@@ -0,0 +1,720 @@
+
+__all__ = [
+    'BaseConstructor',
+    'SafeConstructor',
+    'FullConstructor',
+    'UnsafeConstructor',
+    'Constructor',
+    'ConstructorError'
+]
+
+from .error import *
+from .nodes import *
+
+import collections.abc, datetime, base64, binascii, re, sys, types
+
+class ConstructorError(MarkedYAMLError):
+    pass
+
+class BaseConstructor:
+
+    yaml_constructors = {}
+    yaml_multi_constructors = {}
+
+    def __init__(self):
+        self.constructed_objects = {}
+        self.recursive_objects = {}
+        self.state_generators = []
+        self.deep_construct = False
+
+    def check_data(self):
+        # If there are more documents available?
+        return self.check_node()
+
+    def get_data(self):
+        # Construct and return the next document.
+        if self.check_node():
+            return self.construct_document(self.get_node())
+
+    def get_single_data(self):
+        # Ensure that the stream contains a single document and construct it.
+        node = self.get_single_node()
+        if node is not None:
+            return self.construct_document(node)
+        return None
+
+    def construct_document(self, node):
+        data = self.construct_object(node)
+        while self.state_generators:
+            state_generators = self.state_generators
+            self.state_generators = []
+            for generator in state_generators:
+                for dummy in generator:
+                    pass
+        self.constructed_objects = {}
+        self.recursive_objects = {}
+        self.deep_construct = False
+        return data
+
+    def construct_object(self, node, deep=False):
+        if node in self.constructed_objects:
+            return self.constructed_objects[node]
+        if deep:
+            old_deep = self.deep_construct
+            self.deep_construct = True
+        if node in self.recursive_objects:
+            raise ConstructorError(None, None,
+                    "found unconstructable recursive node", node.start_mark)
+        self.recursive_objects[node] = None
+        constructor = None
+        tag_suffix = None
+        if node.tag in self.yaml_constructors:
+            constructor = self.yaml_constructors[node.tag]
+        else:
+            for tag_prefix in self.yaml_multi_constructors:
+                if node.tag.startswith(tag_prefix):
+                    tag_suffix = node.tag[len(tag_prefix):]
+                    constructor = self.yaml_multi_constructors[tag_prefix]
+                    break
+            else:
+                if None in self.yaml_multi_constructors:
+                    tag_suffix = node.tag
+                    constructor = self.yaml_multi_constructors[None]
+                elif None in self.yaml_constructors:
+                    constructor = self.yaml_constructors[None]
+                elif isinstance(node, ScalarNode):
+                    constructor = self.__class__.construct_scalar
+                elif isinstance(node, SequenceNode):
+                    constructor = self.__class__.construct_sequence
+                elif isinstance(node, MappingNode):
+                    constructor = self.__class__.construct_mapping
+        if tag_suffix is None:
+            data = constructor(self, node)
+        else:
+            data = constructor(self, tag_suffix, node)
+        if isinstance(data, types.GeneratorType):
+            generator = data
+            data = next(generator)
+            if self.deep_construct:
+                for dummy in generator:
+                    pass
+            else:
+                self.state_generators.append(generator)
+        self.constructed_objects[node] = data
+        del self.recursive_objects[node]
+        if deep:
+            self.deep_construct = old_deep
+        return data
+
+    def construct_scalar(self, node):
+        if not isinstance(node, ScalarNode):
+            raise ConstructorError(None, None,
+                    "expected a scalar node, but found %s" % node.id,
+                    node.start_mark)
+        return node.value
+
+    def construct_sequence(self, node, deep=False):
+        if not isinstance(node, SequenceNode):
+            raise ConstructorError(None, None,
+                    "expected a sequence node, but found %s" % node.id,
+                    node.start_mark)
+        return [self.construct_object(child, deep=deep)
+                for child in node.value]
+
+    def construct_mapping(self, node, deep=False):
+        if not isinstance(node, MappingNode):
+            raise ConstructorError(None, None,
+                    "expected a mapping node, but found %s" % node.id,
+                    node.start_mark)
+        mapping = {}
+        for key_node, value_node in node.value:
+            key = self.construct_object(key_node, deep=deep)
+            if not isinstance(key, collections.abc.Hashable):
+                raise ConstructorError("while constructing a mapping", node.start_mark,
+                        "found unhashable key", key_node.start_mark)
+            value = self.construct_object(value_node, deep=deep)
+            mapping[key] = value
+        return mapping
+
+    def construct_pairs(self, node, deep=False):
+        if not isinstance(node, MappingNode):
+            raise ConstructorError(None, None,
+                    "expected a mapping node, but found %s" % node.id,
+                    node.start_mark)
+        pairs = []
+        for key_node, value_node in node.value:
+            key = self.construct_object(key_node, deep=deep)
+            value = self.construct_object(value_node, deep=deep)
+            pairs.append((key, value))
+        return pairs
+
+    @classmethod
+    def add_constructor(cls, tag, constructor):
+        if not 'yaml_constructors' in cls.__dict__:
+            cls.yaml_constructors = cls.yaml_constructors.copy()
+        cls.yaml_constructors[tag] = constructor
+
+    @classmethod
+    def add_multi_constructor(cls, tag_prefix, multi_constructor):
+        if not 'yaml_multi_constructors' in cls.__dict__:
+            cls.yaml_multi_constructors = cls.yaml_multi_constructors.copy()
+        cls.yaml_multi_constructors[tag_prefix] = multi_constructor
+
+class SafeConstructor(BaseConstructor):
+
+    def construct_scalar(self, node):
+        if isinstance(node, MappingNode):
+            for key_node, value_node in node.value:
+                if key_node.tag == 'tag:yaml.org,2002:value':
+                    return self.construct_scalar(value_node)
+        return super().construct_scalar(node)
+
+    def flatten_mapping(self, node):
+        merge = []
+        index = 0
+        while index < len(node.value):
+            key_node, value_node = node.value[index]
+            if key_node.tag == 'tag:yaml.org,2002:merge':
+                del node.value[index]
+                if isinstance(value_node, MappingNode):
+                    self.flatten_mapping(value_node)
+                    merge.extend(value_node.value)
+                elif isinstance(value_node, SequenceNode):
+                    submerge = []
+                    for subnode in value_node.value:
+                        if not isinstance(subnode, MappingNode):
+                            raise ConstructorError("while constructing a mapping",
+                                    node.start_mark,
+                                    "expected a mapping for merging, but found %s"
+                                    % subnode.id, subnode.start_mark)
+                        self.flatten_mapping(subnode)
+                        submerge.append(subnode.value)
+                    submerge.reverse()
+                    for value in submerge:
+                        merge.extend(value)
+                else:
+                    raise ConstructorError("while constructing a mapping", node.start_mark,
+                            "expected a mapping or list of mappings for merging, but found %s"
+                            % value_node.id, value_node.start_mark)
+            elif key_node.tag == 'tag:yaml.org,2002:value':
+                key_node.tag = 'tag:yaml.org,2002:str'
+                index += 1
+            else:
+                index += 1
+        if merge:
+            node.value = merge + node.value
+
+    def construct_mapping(self, node, deep=False):
+        if isinstance(node, MappingNode):
+            self.flatten_mapping(node)
+        return super().construct_mapping(node, deep=deep)
+
+    def construct_yaml_null(self, node):
+        self.construct_scalar(node)
+        return None
+
+    bool_values = {
+        'yes':      True,
+        'no':       False,
+        'true':     True,
+        'false':    False,
+        'on':       True,
+        'off':      False,
+    }
+
+    def construct_yaml_bool(self, node):
+        value = self.construct_scalar(node)
+        return self.bool_values[value.lower()]
+
+    def construct_yaml_int(self, node):
+        value = self.construct_scalar(node)
+        value = value.replace('_', '')
+        sign = +1
+        if value[0] == '-':
+            sign = -1
+        if value[0] in '+-':
+            value = value[1:]
+        if value == '0':
+            return 0
+        elif value.startswith('0b'):
+            return sign*int(value[2:], 2)
+        elif value.startswith('0x'):
+            return sign*int(value[2:], 16)
+        elif value[0] == '0':
+            return sign*int(value, 8)
+        elif ':' in value:
+            digits = [int(part) for part in value.split(':')]
+            digits.reverse()
+            base = 1
+            value = 0
+            for digit in digits:
+                value += digit*base
+                base *= 60
+            return sign*value
+        else:
+            return sign*int(value)
+
+    inf_value = 1e300
+    while inf_value != inf_value*inf_value:
+        inf_value *= inf_value
+    nan_value = -inf_value/inf_value   # Trying to make a quiet NaN (like C99).
+
+    def construct_yaml_float(self, node):
+        value = self.construct_scalar(node)
+        value = value.replace('_', '').lower()
+        sign = +1
+        if value[0] == '-':
+            sign = -1
+        if value[0] in '+-':
+            value = value[1:]
+        if value == '.inf':
+            return sign*self.inf_value
+        elif value == '.nan':
+            return self.nan_value
+        elif ':' in value:
+            digits = [float(part) for part in value.split(':')]
+            digits.reverse()
+            base = 1
+            value = 0.0
+            for digit in digits:
+                value += digit*base
+                base *= 60
+            return sign*value
+        else:
+            return sign*float(value)
+
+    def construct_yaml_binary(self, node):
+        try:
+            value = self.construct_scalar(node).encode('ascii')
+        except UnicodeEncodeError as exc:
+            raise ConstructorError(None, None,
+                    "failed to convert base64 data into ascii: %s" % exc,
+                    node.start_mark)
+        try:
+            if hasattr(base64, 'decodebytes'):
+                return base64.decodebytes(value)
+            else:
+                return base64.decodestring(value)
+        except binascii.Error as exc:
+            raise ConstructorError(None, None,
+                    "failed to decode base64 data: %s" % exc, node.start_mark)
+
+    timestamp_regexp = re.compile(
+            r'''^(?P<year>[0-9][0-9][0-9][0-9])
+                -(?P<month>[0-9][0-9]?)
+                -(?P<day>[0-9][0-9]?)
+                (?:(?:[Tt]|[ \t]+)
+                (?P<hour>[0-9][0-9]?)
+                :(?P<minute>[0-9][0-9])
+                :(?P<second>[0-9][0-9])
+                (?:\.(?P<fraction>[0-9]*))?
+                (?:[ \t]*(?P<tz>Z|(?P<tz_sign>[-+])(?P<tz_hour>[0-9][0-9]?)
+                (?::(?P<tz_minute>[0-9][0-9]))?))?)?$''', re.X)
+
+    def construct_yaml_timestamp(self, node):
+        value = self.construct_scalar(node)
+        match = self.timestamp_regexp.match(node.value)
+        values = match.groupdict()
+        year = int(values['year'])
+        month = int(values['month'])
+        day = int(values['day'])
+        if not values['hour']:
+            return datetime.date(year, month, day)
+        hour = int(values['hour'])
+        minute = int(values['minute'])
+        second = int(values['second'])
+        fraction = 0
+        if values['fraction']:
+            fraction = values['fraction'][:6]
+            while len(fraction) < 6:
+                fraction += '0'
+            fraction = int(fraction)
+        delta = None
+        if values['tz_sign']:
+            tz_hour = int(values['tz_hour'])
+            tz_minute = int(values['tz_minute'] or 0)
+            delta = datetime.timedelta(hours=tz_hour, minutes=tz_minute)
+            if values['tz_sign'] == '-':
+                delta = -delta
+        data = datetime.datetime(year, month, day, hour, minute, second, fraction)
+        if delta:
+            data -= delta
+        return data
+
+    def construct_yaml_omap(self, node):
+        # Note: we do not check for duplicate keys, because it's too
+        # CPU-expensive.
+        omap = []
+        yield omap
+        if not isinstance(node, SequenceNode):
+            raise ConstructorError("while constructing an ordered map", node.start_mark,
+                    "expected a sequence, but found %s" % node.id, node.start_mark)
+        for subnode in node.value:
+            if not isinstance(subnode, MappingNode):
+                raise ConstructorError("while constructing an ordered map", node.start_mark,
+                        "expected a mapping of length 1, but found %s" % subnode.id,
+                        subnode.start_mark)
+            if len(subnode.value) != 1:
+                raise ConstructorError("while constructing an ordered map", node.start_mark,
+                        "expected a single mapping item, but found %d items" % len(subnode.value),
+                        subnode.start_mark)
+            key_node, value_node = subnode.value[0]
+            key = self.construct_object(key_node)
+            value = self.construct_object(value_node)
+            omap.append((key, value))
+
+    def construct_yaml_pairs(self, node):
+        # Note: the same code as `construct_yaml_omap`.
+        pairs = []
+        yield pairs
+        if not isinstance(node, SequenceNode):
+            raise ConstructorError("while constructing pairs", node.start_mark,
+                    "expected a sequence, but found %s" % node.id, node.start_mark)
+        for subnode in node.value:
+            if not isinstance(subnode, MappingNode):
+                raise ConstructorError("while constructing pairs", node.start_mark,
+                        "expected a mapping of length 1, but found %s" % subnode.id,
+                        subnode.start_mark)
+            if len(subnode.value) != 1:
+                raise ConstructorError("while constructing pairs", node.start_mark,
+                        "expected a single mapping item, but found %d items" % len(subnode.value),
+                        subnode.start_mark)
+            key_node, value_node = subnode.value[0]
+            key = self.construct_object(key_node)
+            value = self.construct_object(value_node)
+            pairs.append((key, value))
+
+    def construct_yaml_set(self, node):
+        data = set()
+        yield data
+        value = self.construct_mapping(node)
+        data.update(value)
+
+    def construct_yaml_str(self, node):
+        return self.construct_scalar(node)
+
+    def construct_yaml_seq(self, node):
+        data = []
+        yield data
+        data.extend(self.construct_sequence(node))
+
+    def construct_yaml_map(self, node):
+        data = {}
+        yield data
+        value = self.construct_mapping(node)
+        data.update(value)
+
+    def construct_yaml_object(self, node, cls):
+        data = cls.__new__(cls)
+        yield data
+        if hasattr(data, '__setstate__'):
+            state = self.construct_mapping(node, deep=True)
+            data.__setstate__(state)
+        else:
+            state = self.construct_mapping(node)
+            data.__dict__.update(state)
+
+    def construct_undefined(self, node):
+        raise ConstructorError(None, None,
+                "could not determine a constructor for the tag %r" % node.tag,
+                node.start_mark)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:null',
+        SafeConstructor.construct_yaml_null)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:bool',
+        SafeConstructor.construct_yaml_bool)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:int',
+        SafeConstructor.construct_yaml_int)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:float',
+        SafeConstructor.construct_yaml_float)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:binary',
+        SafeConstructor.construct_yaml_binary)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:timestamp',
+        SafeConstructor.construct_yaml_timestamp)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:omap',
+        SafeConstructor.construct_yaml_omap)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:pairs',
+        SafeConstructor.construct_yaml_pairs)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:set',
+        SafeConstructor.construct_yaml_set)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:str',
+        SafeConstructor.construct_yaml_str)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:seq',
+        SafeConstructor.construct_yaml_seq)
+
+SafeConstructor.add_constructor(
+        'tag:yaml.org,2002:map',
+        SafeConstructor.construct_yaml_map)
+
+SafeConstructor.add_constructor(None,
+        SafeConstructor.construct_undefined)
+
+class FullConstructor(SafeConstructor):
+
+    def construct_python_str(self, node):
+        return self.construct_scalar(node)
+
+    def construct_python_unicode(self, node):
+        return self.construct_scalar(node)
+
+    def construct_python_bytes(self, node):
+        try:
+            value = self.construct_scalar(node).encode('ascii')
+        except UnicodeEncodeError as exc:
+            raise ConstructorError(None, None,
+                    "failed to convert base64 data into ascii: %s" % exc,
+                    node.start_mark)
+        try:
+            if hasattr(base64, 'decodebytes'):
+                return base64.decodebytes(value)
+            else:
+                return base64.decodestring(value)
+        except binascii.Error as exc:
+            raise ConstructorError(None, None,
+                    "failed to decode base64 data: %s" % exc, node.start_mark)
+
+    def construct_python_long(self, node):
+        return self.construct_yaml_int(node)
+
+    def construct_python_complex(self, node):
+       return complex(self.construct_scalar(node))
+
+    def construct_python_tuple(self, node):
+        return tuple(self.construct_sequence(node))
+
+    def find_python_module(self, name, mark, unsafe=False):
+        if not name:
+            raise ConstructorError("while constructing a Python module", mark,
+                    "expected non-empty name appended to the tag", mark)
+        if unsafe:
+            try:
+                __import__(name)
+            except ImportError as exc:
+                raise ConstructorError("while constructing a Python module", mark,
+                        "cannot find module %r (%s)" % (name, exc), mark)
+        if not name in sys.modules:
+            raise ConstructorError("while constructing a Python module", mark,
+                    "module %r is not imported" % name, mark)
+        return sys.modules[name]
+
+    def find_python_name(self, name, mark, unsafe=False):
+        if not name:
+            raise ConstructorError("while constructing a Python object", mark,
+                    "expected non-empty name appended to the tag", mark)
+        if '.' in name:
+            module_name, object_name = name.rsplit('.', 1)
+        else:
+            module_name = 'builtins'
+            object_name = name
+        if unsafe:
+            try:
+                __import__(module_name)
+            except ImportError as exc:
+                raise ConstructorError("while constructing a Python object", mark,
+                        "cannot find module %r (%s)" % (module_name, exc), mark)
+        if not module_name in sys.modules:
+            raise ConstructorError("while constructing a Python object", mark,
+                    "module %r is not imported" % module_name, mark)
+        module = sys.modules[module_name]
+        if not hasattr(module, object_name):
+            raise ConstructorError("while constructing a Python object", mark,
+                    "cannot find %r in the module %r"
+                    % (object_name, module.__name__), mark)
+        return getattr(module, object_name)
+
+    def construct_python_name(self, suffix, node):
+        value = self.construct_scalar(node)
+        if value:
+            raise ConstructorError("while constructing a Python name", node.start_mark,
+                    "expected the empty value, but found %r" % value, node.start_mark)
+        return self.find_python_name(suffix, node.start_mark)
+
+    def construct_python_module(self, suffix, node):
+        value = self.construct_scalar(node)
+        if value:
+            raise ConstructorError("while constructing a Python module", node.start_mark,
+                    "expected the empty value, but found %r" % value, node.start_mark)
+        return self.find_python_module(suffix, node.start_mark)
+
+    def make_python_instance(self, suffix, node,
+            args=None, kwds=None, newobj=False, unsafe=False):
+        if not args:
+            args = []
+        if not kwds:
+            kwds = {}
+        cls = self.find_python_name(suffix, node.start_mark)
+        if not (unsafe or isinstance(cls, type)):
+            raise ConstructorError("while constructing a Python instance", node.start_mark,
+                    "expected a class, but found %r" % type(cls),
+                    node.start_mark)
+        if newobj and isinstance(cls, type):
+            return cls.__new__(cls, *args, **kwds)
+        else:
+            return cls(*args, **kwds)
+
+    def set_python_instance_state(self, instance, state):
+        if hasattr(instance, '__setstate__'):
+            instance.__setstate__(state)
+        else:
+            slotstate = {}
+            if isinstance(state, tuple) and len(state) == 2:
+                state, slotstate = state
+            if hasattr(instance, '__dict__'):
+                instance.__dict__.update(state)
+            elif state:
+                slotstate.update(state)
+            for key, value in slotstate.items():
+                setattr(object, key, value)
+
+    def construct_python_object(self, suffix, node):
+        # Format:
+        #   !!python/object:module.name { ... state ... }
+        instance = self.make_python_instance(suffix, node, newobj=True)
+        yield instance
+        deep = hasattr(instance, '__setstate__')
+        state = self.construct_mapping(node, deep=deep)
+        self.set_python_instance_state(instance, state)
+
+    def construct_python_object_apply(self, suffix, node, newobj=False):
+        # Format:
+        #   !!python/object/apply       # (or !!python/object/new)
+        #   args: [ ... arguments ... ]
+        #   kwds: { ... keywords ... }
+        #   state: ... state ...
+        #   listitems: [ ... listitems ... ]
+        #   dictitems: { ... dictitems ... }
+        # or short format:
+        #   !!python/object/apply [ ... arguments ... ]
+        # The difference between !!python/object/apply and !!python/object/new
+        # is how an object is created, check make_python_instance for details.
+        if isinstance(node, SequenceNode):
+            args = self.construct_sequence(node, deep=True)
+            kwds = {}
+            state = {}
+            listitems = []
+            dictitems = {}
+        else:
+            value = self.construct_mapping(node, deep=True)
+            args = value.get('args', [])
+            kwds = value.get('kwds', {})
+            state = value.get('state', {})
+            listitems = value.get('listitems', [])
+            dictitems = value.get('dictitems', {})
+        instance = self.make_python_instance(suffix, node, args, kwds, newobj)
+        if state:
+            self.set_python_instance_state(instance, state)
+        if listitems:
+            instance.extend(listitems)
+        if dictitems:
+            for key in dictitems:
+                instance[key] = dictitems[key]
+        return instance
+
+    def construct_python_object_new(self, suffix, node):
+        return self.construct_python_object_apply(suffix, node, newobj=True)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/none',
+    FullConstructor.construct_yaml_null)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/bool',
+    FullConstructor.construct_yaml_bool)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/str',
+    FullConstructor.construct_python_str)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/unicode',
+    FullConstructor.construct_python_unicode)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/bytes',
+    FullConstructor.construct_python_bytes)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/int',
+    FullConstructor.construct_yaml_int)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/long',
+    FullConstructor.construct_python_long)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/float',
+    FullConstructor.construct_yaml_float)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/complex',
+    FullConstructor.construct_python_complex)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/list',
+    FullConstructor.construct_yaml_seq)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/tuple',
+    FullConstructor.construct_python_tuple)
+
+FullConstructor.add_constructor(
+    'tag:yaml.org,2002:python/dict',
+    FullConstructor.construct_yaml_map)
+
+FullConstructor.add_multi_constructor(
+    'tag:yaml.org,2002:python/name:',
+    FullConstructor.construct_python_name)
+
+FullConstructor.add_multi_constructor(
+    'tag:yaml.org,2002:python/module:',
+    FullConstructor.construct_python_module)
+
+FullConstructor.add_multi_constructor(
+    'tag:yaml.org,2002:python/object:',
+    FullConstructor.construct_python_object)
+
+FullConstructor.add_multi_constructor(
+    'tag:yaml.org,2002:python/object/apply:',
+    FullConstructor.construct_python_object_apply)
+
+FullConstructor.add_multi_constructor(
+    'tag:yaml.org,2002:python/object/new:',
+    FullConstructor.construct_python_object_new)
+
+class UnsafeConstructor(FullConstructor):
+
+    def find_python_module(self, name, mark):
+        return super(UnsafeConstructor, self).find_python_module(name, mark, unsafe=True)
+
+    def find_python_name(self, name, mark):
+        return super(UnsafeConstructor, self).find_python_name(name, mark, unsafe=True)
+
+    def make_python_instance(self, suffix, node, args=None, kwds=None, newobj=False):
+        return super(UnsafeConstructor, self).make_python_instance(
+            suffix, node, args, kwds, newobj, unsafe=True)
+
+# Constructor is same as UnsafeConstructor. Need to leave this in place in case
+# people have extended it directly.
+class Constructor(UnsafeConstructor):
+    pass
diff --git a/libs/yaml/cyaml.py b/libs/yaml/cyaml.py
new file mode 100644
index 000000000..1e606c74b
--- /dev/null
+++ b/libs/yaml/cyaml.py
@@ -0,0 +1,101 @@
+
+__all__ = [
+    'CBaseLoader', 'CSafeLoader', 'CFullLoader', 'CUnsafeLoader', 'CLoader',
+    'CBaseDumper', 'CSafeDumper', 'CDumper'
+]
+
+from _yaml import CParser, CEmitter
+
+from .constructor import *
+
+from .serializer import *
+from .representer import *
+
+from .resolver import *
+
+class CBaseLoader(CParser, BaseConstructor, BaseResolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        BaseConstructor.__init__(self)
+        BaseResolver.__init__(self)
+
+class CSafeLoader(CParser, SafeConstructor, Resolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        SafeConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class CFullLoader(CParser, FullConstructor, Resolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        FullConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class CUnsafeLoader(CParser, UnsafeConstructor, Resolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        UnsafeConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class CLoader(CParser, Constructor, Resolver):
+
+    def __init__(self, stream):
+        CParser.__init__(self, stream)
+        Constructor.__init__(self)
+        Resolver.__init__(self)
+
+class CBaseDumper(CEmitter, BaseRepresenter, BaseResolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        CEmitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width, encoding=encoding,
+                allow_unicode=allow_unicode, line_break=line_break,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        Resolver.__init__(self)
+
+class CSafeDumper(CEmitter, SafeRepresenter, Resolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        CEmitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width, encoding=encoding,
+                allow_unicode=allow_unicode, line_break=line_break,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        SafeRepresenter.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        Resolver.__init__(self)
+
+class CDumper(CEmitter, Serializer, Representer, Resolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        CEmitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width, encoding=encoding,
+                allow_unicode=allow_unicode, line_break=line_break,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        Resolver.__init__(self)
+
diff --git a/libs/yaml/dumper.py b/libs/yaml/dumper.py
new file mode 100644
index 000000000..6aadba551
--- /dev/null
+++ b/libs/yaml/dumper.py
@@ -0,0 +1,62 @@
+
+__all__ = ['BaseDumper', 'SafeDumper', 'Dumper']
+
+from .emitter import *
+from .serializer import *
+from .representer import *
+from .resolver import *
+
+class BaseDumper(Emitter, Serializer, BaseRepresenter, BaseResolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        Resolver.__init__(self)
+
+class SafeDumper(Emitter, Serializer, SafeRepresenter, Resolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        SafeRepresenter.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        Resolver.__init__(self)
+
+class Dumper(Emitter, Serializer, Representer, Resolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        Representer.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        Resolver.__init__(self)
+
diff --git a/libs/yaml/emitter.py b/libs/yaml/emitter.py
new file mode 100644
index 000000000..a664d0111
--- /dev/null
+++ b/libs/yaml/emitter.py
@@ -0,0 +1,1137 @@
+
+# Emitter expects events obeying the following grammar:
+# stream ::= STREAM-START document* STREAM-END
+# document ::= DOCUMENT-START node DOCUMENT-END
+# node ::= SCALAR | sequence | mapping
+# sequence ::= SEQUENCE-START node* SEQUENCE-END
+# mapping ::= MAPPING-START (node node)* MAPPING-END
+
+__all__ = ['Emitter', 'EmitterError']
+
+from .error import YAMLError
+from .events import *
+
+class EmitterError(YAMLError):
+    pass
+
+class ScalarAnalysis:
+    def __init__(self, scalar, empty, multiline,
+            allow_flow_plain, allow_block_plain,
+            allow_single_quoted, allow_double_quoted,
+            allow_block):
+        self.scalar = scalar
+        self.empty = empty
+        self.multiline = multiline
+        self.allow_flow_plain = allow_flow_plain
+        self.allow_block_plain = allow_block_plain
+        self.allow_single_quoted = allow_single_quoted
+        self.allow_double_quoted = allow_double_quoted
+        self.allow_block = allow_block
+
+class Emitter:
+
+    DEFAULT_TAG_PREFIXES = {
+        '!' : '!',
+        'tag:yaml.org,2002:' : '!!',
+    }
+
+    def __init__(self, stream, canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None):
+
+        # The stream should have the methods `write` and possibly `flush`.
+        self.stream = stream
+
+        # Encoding can be overridden by STREAM-START.
+        self.encoding = None
+
+        # Emitter is a state machine with a stack of states to handle nested
+        # structures.
+        self.states = []
+        self.state = self.expect_stream_start
+
+        # Current event and the event queue.
+        self.events = []
+        self.event = None
+
+        # The current indentation level and the stack of previous indents.
+        self.indents = []
+        self.indent = None
+
+        # Flow level.
+        self.flow_level = 0
+
+        # Contexts.
+        self.root_context = False
+        self.sequence_context = False
+        self.mapping_context = False
+        self.simple_key_context = False
+
+        # Characteristics of the last emitted character:
+        #  - current position.
+        #  - is it a whitespace?
+        #  - is it an indention character
+        #    (indentation space, '-', '?', or ':')?
+        self.line = 0
+        self.column = 0
+        self.whitespace = True
+        self.indention = True
+
+        # Whether the document requires an explicit document indicator
+        self.open_ended = False
+
+        # Formatting details.
+        self.canonical = canonical
+        self.allow_unicode = allow_unicode
+        self.best_indent = 2
+        if indent and 1 < indent < 10:
+            self.best_indent = indent
+        self.best_width = 80
+        if width and width > self.best_indent*2:
+            self.best_width = width
+        self.best_line_break = '\n'
+        if line_break in ['\r', '\n', '\r\n']:
+            self.best_line_break = line_break
+
+        # Tag prefixes.
+        self.tag_prefixes = None
+
+        # Prepared anchor and tag.
+        self.prepared_anchor = None
+        self.prepared_tag = None
+
+        # Scalar analysis and style.
+        self.analysis = None
+        self.style = None
+
+    def dispose(self):
+        # Reset the state attributes (to clear self-references)
+        self.states = []
+        self.state = None
+
+    def emit(self, event):
+        self.events.append(event)
+        while not self.need_more_events():
+            self.event = self.events.pop(0)
+            self.state()
+            self.event = None
+
+    # In some cases, we wait for a few next events before emitting.
+
+    def need_more_events(self):
+        if not self.events:
+            return True
+        event = self.events[0]
+        if isinstance(event, DocumentStartEvent):
+            return self.need_events(1)
+        elif isinstance(event, SequenceStartEvent):
+            return self.need_events(2)
+        elif isinstance(event, MappingStartEvent):
+            return self.need_events(3)
+        else:
+            return False
+
+    def need_events(self, count):
+        level = 0
+        for event in self.events[1:]:
+            if isinstance(event, (DocumentStartEvent, CollectionStartEvent)):
+                level += 1
+            elif isinstance(event, (DocumentEndEvent, CollectionEndEvent)):
+                level -= 1
+            elif isinstance(event, StreamEndEvent):
+                level = -1
+            if level < 0:
+                return False
+        return (len(self.events) < count+1)
+
+    def increase_indent(self, flow=False, indentless=False):
+        self.indents.append(self.indent)
+        if self.indent is None:
+            if flow:
+                self.indent = self.best_indent
+            else:
+                self.indent = 0
+        elif not indentless:
+            self.indent += self.best_indent
+
+    # States.
+
+    # Stream handlers.
+
+    def expect_stream_start(self):
+        if isinstance(self.event, StreamStartEvent):
+            if self.event.encoding and not hasattr(self.stream, 'encoding'):
+                self.encoding = self.event.encoding
+            self.write_stream_start()
+            self.state = self.expect_first_document_start
+        else:
+            raise EmitterError("expected StreamStartEvent, but got %s"
+                    % self.event)
+
+    def expect_nothing(self):
+        raise EmitterError("expected nothing, but got %s" % self.event)
+
+    # Document handlers.
+
+    def expect_first_document_start(self):
+        return self.expect_document_start(first=True)
+
+    def expect_document_start(self, first=False):
+        if isinstance(self.event, DocumentStartEvent):
+            if (self.event.version or self.event.tags) and self.open_ended:
+                self.write_indicator('...', True)
+                self.write_indent()
+            if self.event.version:
+                version_text = self.prepare_version(self.event.version)
+                self.write_version_directive(version_text)
+            self.tag_prefixes = self.DEFAULT_TAG_PREFIXES.copy()
+            if self.event.tags:
+                handles = sorted(self.event.tags.keys())
+                for handle in handles:
+                    prefix = self.event.tags[handle]
+                    self.tag_prefixes[prefix] = handle
+                    handle_text = self.prepare_tag_handle(handle)
+                    prefix_text = self.prepare_tag_prefix(prefix)
+                    self.write_tag_directive(handle_text, prefix_text)
+            implicit = (first and not self.event.explicit and not self.canonical
+                    and not self.event.version and not self.event.tags
+                    and not self.check_empty_document())
+            if not implicit:
+                self.write_indent()
+                self.write_indicator('---', True)
+                if self.canonical:
+                    self.write_indent()
+            self.state = self.expect_document_root
+        elif isinstance(self.event, StreamEndEvent):
+            if self.open_ended:
+                self.write_indicator('...', True)
+                self.write_indent()
+            self.write_stream_end()
+            self.state = self.expect_nothing
+        else:
+            raise EmitterError("expected DocumentStartEvent, but got %s"
+                    % self.event)
+
+    def expect_document_end(self):
+        if isinstance(self.event, DocumentEndEvent):
+            self.write_indent()
+            if self.event.explicit:
+                self.write_indicator('...', True)
+                self.write_indent()
+            self.flush_stream()
+            self.state = self.expect_document_start
+        else:
+            raise EmitterError("expected DocumentEndEvent, but got %s"
+                    % self.event)
+
+    def expect_document_root(self):
+        self.states.append(self.expect_document_end)
+        self.expect_node(root=True)
+
+    # Node handlers.
+
+    def expect_node(self, root=False, sequence=False, mapping=False,
+            simple_key=False):
+        self.root_context = root
+        self.sequence_context = sequence
+        self.mapping_context = mapping
+        self.simple_key_context = simple_key
+        if isinstance(self.event, AliasEvent):
+            self.expect_alias()
+        elif isinstance(self.event, (ScalarEvent, CollectionStartEvent)):
+            self.process_anchor('&')
+            self.process_tag()
+            if isinstance(self.event, ScalarEvent):
+                self.expect_scalar()
+            elif isinstance(self.event, SequenceStartEvent):
+                if self.flow_level or self.canonical or self.event.flow_style   \
+                        or self.check_empty_sequence():
+                    self.expect_flow_sequence()
+                else:
+                    self.expect_block_sequence()
+            elif isinstance(self.event, MappingStartEvent):
+                if self.flow_level or self.canonical or self.event.flow_style   \
+                        or self.check_empty_mapping():
+                    self.expect_flow_mapping()
+                else:
+                    self.expect_block_mapping()
+        else:
+            raise EmitterError("expected NodeEvent, but got %s" % self.event)
+
+    def expect_alias(self):
+        if self.event.anchor is None:
+            raise EmitterError("anchor is not specified for alias")
+        self.process_anchor('*')
+        self.state = self.states.pop()
+
+    def expect_scalar(self):
+        self.increase_indent(flow=True)
+        self.process_scalar()
+        self.indent = self.indents.pop()
+        self.state = self.states.pop()
+
+    # Flow sequence handlers.
+
+    def expect_flow_sequence(self):
+        self.write_indicator('[', True, whitespace=True)
+        self.flow_level += 1
+        self.increase_indent(flow=True)
+        self.state = self.expect_first_flow_sequence_item
+
+    def expect_first_flow_sequence_item(self):
+        if isinstance(self.event, SequenceEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            self.write_indicator(']', False)
+            self.state = self.states.pop()
+        else:
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            self.states.append(self.expect_flow_sequence_item)
+            self.expect_node(sequence=True)
+
+    def expect_flow_sequence_item(self):
+        if isinstance(self.event, SequenceEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            if self.canonical:
+                self.write_indicator(',', False)
+                self.write_indent()
+            self.write_indicator(']', False)
+            self.state = self.states.pop()
+        else:
+            self.write_indicator(',', False)
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            self.states.append(self.expect_flow_sequence_item)
+            self.expect_node(sequence=True)
+
+    # Flow mapping handlers.
+
+    def expect_flow_mapping(self):
+        self.write_indicator('{', True, whitespace=True)
+        self.flow_level += 1
+        self.increase_indent(flow=True)
+        self.state = self.expect_first_flow_mapping_key
+
+    def expect_first_flow_mapping_key(self):
+        if isinstance(self.event, MappingEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            self.write_indicator('}', False)
+            self.state = self.states.pop()
+        else:
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            if not self.canonical and self.check_simple_key():
+                self.states.append(self.expect_flow_mapping_simple_value)
+                self.expect_node(mapping=True, simple_key=True)
+            else:
+                self.write_indicator('?', True)
+                self.states.append(self.expect_flow_mapping_value)
+                self.expect_node(mapping=True)
+
+    def expect_flow_mapping_key(self):
+        if isinstance(self.event, MappingEndEvent):
+            self.indent = self.indents.pop()
+            self.flow_level -= 1
+            if self.canonical:
+                self.write_indicator(',', False)
+                self.write_indent()
+            self.write_indicator('}', False)
+            self.state = self.states.pop()
+        else:
+            self.write_indicator(',', False)
+            if self.canonical or self.column > self.best_width:
+                self.write_indent()
+            if not self.canonical and self.check_simple_key():
+                self.states.append(self.expect_flow_mapping_simple_value)
+                self.expect_node(mapping=True, simple_key=True)
+            else:
+                self.write_indicator('?', True)
+                self.states.append(self.expect_flow_mapping_value)
+                self.expect_node(mapping=True)
+
+    def expect_flow_mapping_simple_value(self):
+        self.write_indicator(':', False)
+        self.states.append(self.expect_flow_mapping_key)
+        self.expect_node(mapping=True)
+
+    def expect_flow_mapping_value(self):
+        if self.canonical or self.column > self.best_width:
+            self.write_indent()
+        self.write_indicator(':', True)
+        self.states.append(self.expect_flow_mapping_key)
+        self.expect_node(mapping=True)
+
+    # Block sequence handlers.
+
+    def expect_block_sequence(self):
+        indentless = (self.mapping_context and not self.indention)
+        self.increase_indent(flow=False, indentless=indentless)
+        self.state = self.expect_first_block_sequence_item
+
+    def expect_first_block_sequence_item(self):
+        return self.expect_block_sequence_item(first=True)
+
+    def expect_block_sequence_item(self, first=False):
+        if not first and isinstance(self.event, SequenceEndEvent):
+            self.indent = self.indents.pop()
+            self.state = self.states.pop()
+        else:
+            self.write_indent()
+            self.write_indicator('-', True, indention=True)
+            self.states.append(self.expect_block_sequence_item)
+            self.expect_node(sequence=True)
+
+    # Block mapping handlers.
+
+    def expect_block_mapping(self):
+        self.increase_indent(flow=False)
+        self.state = self.expect_first_block_mapping_key
+
+    def expect_first_block_mapping_key(self):
+        return self.expect_block_mapping_key(first=True)
+
+    def expect_block_mapping_key(self, first=False):
+        if not first and isinstance(self.event, MappingEndEvent):
+            self.indent = self.indents.pop()
+            self.state = self.states.pop()
+        else:
+            self.write_indent()
+            if self.check_simple_key():
+                self.states.append(self.expect_block_mapping_simple_value)
+                self.expect_node(mapping=True, simple_key=True)
+            else:
+                self.write_indicator('?', True, indention=True)
+                self.states.append(self.expect_block_mapping_value)
+                self.expect_node(mapping=True)
+
+    def expect_block_mapping_simple_value(self):
+        self.write_indicator(':', False)
+        self.states.append(self.expect_block_mapping_key)
+        self.expect_node(mapping=True)
+
+    def expect_block_mapping_value(self):
+        self.write_indent()
+        self.write_indicator(':', True, indention=True)
+        self.states.append(self.expect_block_mapping_key)
+        self.expect_node(mapping=True)
+
+    # Checkers.
+
+    def check_empty_sequence(self):
+        return (isinstance(self.event, SequenceStartEvent) and self.events
+                and isinstance(self.events[0], SequenceEndEvent))
+
+    def check_empty_mapping(self):
+        return (isinstance(self.event, MappingStartEvent) and self.events
+                and isinstance(self.events[0], MappingEndEvent))
+
+    def check_empty_document(self):
+        if not isinstance(self.event, DocumentStartEvent) or not self.events:
+            return False
+        event = self.events[0]
+        return (isinstance(event, ScalarEvent) and event.anchor is None
+                and event.tag is None and event.implicit and event.value == '')
+
+    def check_simple_key(self):
+        length = 0
+        if isinstance(self.event, NodeEvent) and self.event.anchor is not None:
+            if self.prepared_anchor is None:
+                self.prepared_anchor = self.prepare_anchor(self.event.anchor)
+            length += len(self.prepared_anchor)
+        if isinstance(self.event, (ScalarEvent, CollectionStartEvent))  \
+                and self.event.tag is not None:
+            if self.prepared_tag is None:
+                self.prepared_tag = self.prepare_tag(self.event.tag)
+            length += len(self.prepared_tag)
+        if isinstance(self.event, ScalarEvent):
+            if self.analysis is None:
+                self.analysis = self.analyze_scalar(self.event.value)
+            length += len(self.analysis.scalar)
+        return (length < 128 and (isinstance(self.event, AliasEvent)
+            or (isinstance(self.event, ScalarEvent)
+                    and not self.analysis.empty and not self.analysis.multiline)
+            or self.check_empty_sequence() or self.check_empty_mapping()))
+
+    # Anchor, Tag, and Scalar processors.
+
+    def process_anchor(self, indicator):
+        if self.event.anchor is None:
+            self.prepared_anchor = None
+            return
+        if self.prepared_anchor is None:
+            self.prepared_anchor = self.prepare_anchor(self.event.anchor)
+        if self.prepared_anchor:
+            self.write_indicator(indicator+self.prepared_anchor, True)
+        self.prepared_anchor = None
+
+    def process_tag(self):
+        tag = self.event.tag
+        if isinstance(self.event, ScalarEvent):
+            if self.style is None:
+                self.style = self.choose_scalar_style()
+            if ((not self.canonical or tag is None) and
+                ((self.style == '' and self.event.implicit[0])
+                        or (self.style != '' and self.event.implicit[1]))):
+                self.prepared_tag = None
+                return
+            if self.event.implicit[0] and tag is None:
+                tag = '!'
+                self.prepared_tag = None
+        else:
+            if (not self.canonical or tag is None) and self.event.implicit:
+                self.prepared_tag = None
+                return
+        if tag is None:
+            raise EmitterError("tag is not specified")
+        if self.prepared_tag is None:
+            self.prepared_tag = self.prepare_tag(tag)
+        if self.prepared_tag:
+            self.write_indicator(self.prepared_tag, True)
+        self.prepared_tag = None
+
+    def choose_scalar_style(self):
+        if self.analysis is None:
+            self.analysis = self.analyze_scalar(self.event.value)
+        if self.event.style == '"' or self.canonical:
+            return '"'
+        if not self.event.style and self.event.implicit[0]:
+            if (not (self.simple_key_context and
+                    (self.analysis.empty or self.analysis.multiline))
+                and (self.flow_level and self.analysis.allow_flow_plain
+                    or (not self.flow_level and self.analysis.allow_block_plain))):
+                return ''
+        if self.event.style and self.event.style in '|>':
+            if (not self.flow_level and not self.simple_key_context
+                    and self.analysis.allow_block):
+                return self.event.style
+        if not self.event.style or self.event.style == '\'':
+            if (self.analysis.allow_single_quoted and
+                    not (self.simple_key_context and self.analysis.multiline)):
+                return '\''
+        return '"'
+
+    def process_scalar(self):
+        if self.analysis is None:
+            self.analysis = self.analyze_scalar(self.event.value)
+        if self.style is None:
+            self.style = self.choose_scalar_style()
+        split = (not self.simple_key_context)
+        #if self.analysis.multiline and split    \
+        #        and (not self.style or self.style in '\'\"'):
+        #    self.write_indent()
+        if self.style == '"':
+            self.write_double_quoted(self.analysis.scalar, split)
+        elif self.style == '\'':
+            self.write_single_quoted(self.analysis.scalar, split)
+        elif self.style == '>':
+            self.write_folded(self.analysis.scalar)
+        elif self.style == '|':
+            self.write_literal(self.analysis.scalar)
+        else:
+            self.write_plain(self.analysis.scalar, split)
+        self.analysis = None
+        self.style = None
+
+    # Analyzers.
+
+    def prepare_version(self, version):
+        major, minor = version
+        if major != 1:
+            raise EmitterError("unsupported YAML version: %d.%d" % (major, minor))
+        return '%d.%d' % (major, minor)
+
+    def prepare_tag_handle(self, handle):
+        if not handle:
+            raise EmitterError("tag handle must not be empty")
+        if handle[0] != '!' or handle[-1] != '!':
+            raise EmitterError("tag handle must start and end with '!': %r" % handle)
+        for ch in handle[1:-1]:
+            if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'    \
+                    or ch in '-_'):
+                raise EmitterError("invalid character %r in the tag handle: %r"
+                        % (ch, handle))
+        return handle
+
+    def prepare_tag_prefix(self, prefix):
+        if not prefix:
+            raise EmitterError("tag prefix must not be empty")
+        chunks = []
+        start = end = 0
+        if prefix[0] == '!':
+            end = 1
+        while end < len(prefix):
+            ch = prefix[end]
+            if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \
+                    or ch in '-;/?!:@&=+$,_.~*\'()[]':
+                end += 1
+            else:
+                if start < end:
+                    chunks.append(prefix[start:end])
+                start = end = end+1
+                data = ch.encode('utf-8')
+                for ch in data:
+                    chunks.append('%%%02X' % ord(ch))
+        if start < end:
+            chunks.append(prefix[start:end])
+        return ''.join(chunks)
+
+    def prepare_tag(self, tag):
+        if not tag:
+            raise EmitterError("tag must not be empty")
+        if tag == '!':
+            return tag
+        handle = None
+        suffix = tag
+        prefixes = sorted(self.tag_prefixes.keys())
+        for prefix in prefixes:
+            if tag.startswith(prefix)   \
+                    and (prefix == '!' or len(prefix) < len(tag)):
+                handle = self.tag_prefixes[prefix]
+                suffix = tag[len(prefix):]
+        chunks = []
+        start = end = 0
+        while end < len(suffix):
+            ch = suffix[end]
+            if '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z' \
+                    or ch in '-;/?:@&=+$,_.~*\'()[]'   \
+                    or (ch == '!' and handle != '!'):
+                end += 1
+            else:
+                if start < end:
+                    chunks.append(suffix[start:end])
+                start = end = end+1
+                data = ch.encode('utf-8')
+                for ch in data:
+                    chunks.append('%%%02X' % ch)
+        if start < end:
+            chunks.append(suffix[start:end])
+        suffix_text = ''.join(chunks)
+        if handle:
+            return '%s%s' % (handle, suffix_text)
+        else:
+            return '!<%s>' % suffix_text
+
+    def prepare_anchor(self, anchor):
+        if not anchor:
+            raise EmitterError("anchor must not be empty")
+        for ch in anchor:
+            if not ('0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'    \
+                    or ch in '-_'):
+                raise EmitterError("invalid character %r in the anchor: %r"
+                        % (ch, anchor))
+        return anchor
+
+    def analyze_scalar(self, scalar):
+
+        # Empty scalar is a special case.
+        if not scalar:
+            return ScalarAnalysis(scalar=scalar, empty=True, multiline=False,
+                    allow_flow_plain=False, allow_block_plain=True,
+                    allow_single_quoted=True, allow_double_quoted=True,
+                    allow_block=False)
+
+        # Indicators and special characters.
+        block_indicators = False
+        flow_indicators = False
+        line_breaks = False
+        special_characters = False
+
+        # Important whitespace combinations.
+        leading_space = False
+        leading_break = False
+        trailing_space = False
+        trailing_break = False
+        break_space = False
+        space_break = False
+
+        # Check document indicators.
+        if scalar.startswith('---') or scalar.startswith('...'):
+            block_indicators = True
+            flow_indicators = True
+
+        # First character or preceded by a whitespace.
+        preceded_by_whitespace = True
+
+        # Last character or followed by a whitespace.
+        followed_by_whitespace = (len(scalar) == 1 or
+                scalar[1] in '\0 \t\r\n\x85\u2028\u2029')
+
+        # The previous character is a space.
+        previous_space = False
+
+        # The previous character is a break.
+        previous_break = False
+
+        index = 0
+        while index < len(scalar):
+            ch = scalar[index]
+
+            # Check for indicators.
+            if index == 0:
+                # Leading indicators are special characters.
+                if ch in '#,[]{}&*!|>\'\"%@`':
+                    flow_indicators = True
+                    block_indicators = True
+                if ch in '?:':
+                    flow_indicators = True
+                    if followed_by_whitespace:
+                        block_indicators = True
+                if ch == '-' and followed_by_whitespace:
+                    flow_indicators = True
+                    block_indicators = True
+            else:
+                # Some indicators cannot appear within a scalar as well.
+                if ch in ',?[]{}':
+                    flow_indicators = True
+                if ch == ':':
+                    flow_indicators = True
+                    if followed_by_whitespace:
+                        block_indicators = True
+                if ch == '#' and preceded_by_whitespace:
+                    flow_indicators = True
+                    block_indicators = True
+
+            # Check for line breaks, special, and unicode characters.
+            if ch in '\n\x85\u2028\u2029':
+                line_breaks = True
+            if not (ch == '\n' or '\x20' <= ch <= '\x7E'):
+                if (ch == '\x85' or '\xA0' <= ch <= '\uD7FF'
+                        or '\uE000' <= ch <= '\uFFFD'
+                        or '\U00010000' <= ch < '\U0010ffff') and ch != '\uFEFF':
+                    unicode_characters = True
+                    if not self.allow_unicode:
+                        special_characters = True
+                else:
+                    special_characters = True
+
+            # Detect important whitespace combinations.
+            if ch == ' ':
+                if index == 0:
+                    leading_space = True
+                if index == len(scalar)-1:
+                    trailing_space = True
+                if previous_break:
+                    break_space = True
+                previous_space = True
+                previous_break = False
+            elif ch in '\n\x85\u2028\u2029':
+                if index == 0:
+                    leading_break = True
+                if index == len(scalar)-1:
+                    trailing_break = True
+                if previous_space:
+                    space_break = True
+                previous_space = False
+                previous_break = True
+            else:
+                previous_space = False
+                previous_break = False
+
+            # Prepare for the next character.
+            index += 1
+            preceded_by_whitespace = (ch in '\0 \t\r\n\x85\u2028\u2029')
+            followed_by_whitespace = (index+1 >= len(scalar) or
+                    scalar[index+1] in '\0 \t\r\n\x85\u2028\u2029')
+
+        # Let's decide what styles are allowed.
+        allow_flow_plain = True
+        allow_block_plain = True
+        allow_single_quoted = True
+        allow_double_quoted = True
+        allow_block = True
+
+        # Leading and trailing whitespaces are bad for plain scalars.
+        if (leading_space or leading_break
+                or trailing_space or trailing_break):
+            allow_flow_plain = allow_block_plain = False
+
+        # We do not permit trailing spaces for block scalars.
+        if trailing_space:
+            allow_block = False
+
+        # Spaces at the beginning of a new line are only acceptable for block
+        # scalars.
+        if break_space:
+            allow_flow_plain = allow_block_plain = allow_single_quoted = False
+
+        # Spaces followed by breaks, as well as special character are only
+        # allowed for double quoted scalars.
+        if space_break or special_characters:
+            allow_flow_plain = allow_block_plain =  \
+            allow_single_quoted = allow_block = False
+
+        # Although the plain scalar writer supports breaks, we never emit
+        # multiline plain scalars.
+        if line_breaks:
+            allow_flow_plain = allow_block_plain = False
+
+        # Flow indicators are forbidden for flow plain scalars.
+        if flow_indicators:
+            allow_flow_plain = False
+
+        # Block indicators are forbidden for block plain scalars.
+        if block_indicators:
+            allow_block_plain = False
+
+        return ScalarAnalysis(scalar=scalar,
+                empty=False, multiline=line_breaks,
+                allow_flow_plain=allow_flow_plain,
+                allow_block_plain=allow_block_plain,
+                allow_single_quoted=allow_single_quoted,
+                allow_double_quoted=allow_double_quoted,
+                allow_block=allow_block)
+
+    # Writers.
+
+    def flush_stream(self):
+        if hasattr(self.stream, 'flush'):
+            self.stream.flush()
+
+    def write_stream_start(self):
+        # Write BOM if needed.
+        if self.encoding and self.encoding.startswith('utf-16'):
+            self.stream.write('\uFEFF'.encode(self.encoding))
+
+    def write_stream_end(self):
+        self.flush_stream()
+
+    def write_indicator(self, indicator, need_whitespace,
+            whitespace=False, indention=False):
+        if self.whitespace or not need_whitespace:
+            data = indicator
+        else:
+            data = ' '+indicator
+        self.whitespace = whitespace
+        self.indention = self.indention and indention
+        self.column += len(data)
+        self.open_ended = False
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+
+    def write_indent(self):
+        indent = self.indent or 0
+        if not self.indention or self.column > indent   \
+                or (self.column == indent and not self.whitespace):
+            self.write_line_break()
+        if self.column < indent:
+            self.whitespace = True
+            data = ' '*(indent-self.column)
+            self.column = indent
+            if self.encoding:
+                data = data.encode(self.encoding)
+            self.stream.write(data)
+
+    def write_line_break(self, data=None):
+        if data is None:
+            data = self.best_line_break
+        self.whitespace = True
+        self.indention = True
+        self.line += 1
+        self.column = 0
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+
+    def write_version_directive(self, version_text):
+        data = '%%YAML %s' % version_text
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+        self.write_line_break()
+
+    def write_tag_directive(self, handle_text, prefix_text):
+        data = '%%TAG %s %s' % (handle_text, prefix_text)
+        if self.encoding:
+            data = data.encode(self.encoding)
+        self.stream.write(data)
+        self.write_line_break()
+
+    # Scalar streams.
+
+    def write_single_quoted(self, text, split=True):
+        self.write_indicator('\'', True)
+        spaces = False
+        breaks = False
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if spaces:
+                if ch is None or ch != ' ':
+                    if start+1 == end and self.column > self.best_width and split   \
+                            and start != 0 and end != len(text):
+                        self.write_indent()
+                    else:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                    start = end
+            elif breaks:
+                if ch is None or ch not in '\n\x85\u2028\u2029':
+                    if text[start] == '\n':
+                        self.write_line_break()
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    self.write_indent()
+                    start = end
+            else:
+                if ch is None or ch in ' \n\x85\u2028\u2029' or ch == '\'':
+                    if start < end:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                        start = end
+            if ch == '\'':
+                data = '\'\''
+                self.column += 2
+                if self.encoding:
+                    data = data.encode(self.encoding)
+                self.stream.write(data)
+                start = end + 1
+            if ch is not None:
+                spaces = (ch == ' ')
+                breaks = (ch in '\n\x85\u2028\u2029')
+            end += 1
+        self.write_indicator('\'', False)
+
+    ESCAPE_REPLACEMENTS = {
+        '\0':       '0',
+        '\x07':     'a',
+        '\x08':     'b',
+        '\x09':     't',
+        '\x0A':     'n',
+        '\x0B':     'v',
+        '\x0C':     'f',
+        '\x0D':     'r',
+        '\x1B':     'e',
+        '\"':       '\"',
+        '\\':       '\\',
+        '\x85':     'N',
+        '\xA0':     '_',
+        '\u2028':   'L',
+        '\u2029':   'P',
+    }
+
+    def write_double_quoted(self, text, split=True):
+        self.write_indicator('"', True)
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if ch is None or ch in '"\\\x85\u2028\u2029\uFEFF' \
+                    or not ('\x20' <= ch <= '\x7E'
+                        or (self.allow_unicode
+                            and ('\xA0' <= ch <= '\uD7FF'
+                                or '\uE000' <= ch <= '\uFFFD'))):
+                if start < end:
+                    data = text[start:end]
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    start = end
+                if ch is not None:
+                    if ch in self.ESCAPE_REPLACEMENTS:
+                        data = '\\'+self.ESCAPE_REPLACEMENTS[ch]
+                    elif ch <= '\xFF':
+                        data = '\\x%02X' % ord(ch)
+                    elif ch <= '\uFFFF':
+                        data = '\\u%04X' % ord(ch)
+                    else:
+                        data = '\\U%08X' % ord(ch)
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    start = end+1
+            if 0 < end < len(text)-1 and (ch == ' ' or start >= end)    \
+                    and self.column+(end-start) > self.best_width and split:
+                data = text[start:end]+'\\'
+                if start < end:
+                    start = end
+                self.column += len(data)
+                if self.encoding:
+                    data = data.encode(self.encoding)
+                self.stream.write(data)
+                self.write_indent()
+                self.whitespace = False
+                self.indention = False
+                if text[start] == ' ':
+                    data = '\\'
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+            end += 1
+        self.write_indicator('"', False)
+
+    def determine_block_hints(self, text):
+        hints = ''
+        if text:
+            if text[0] in ' \n\x85\u2028\u2029':
+                hints += str(self.best_indent)
+            if text[-1] not in '\n\x85\u2028\u2029':
+                hints += '-'
+            elif len(text) == 1 or text[-2] in '\n\x85\u2028\u2029':
+                hints += '+'
+        return hints
+
+    def write_folded(self, text):
+        hints = self.determine_block_hints(text)
+        self.write_indicator('>'+hints, True)
+        if hints[-1:] == '+':
+            self.open_ended = True
+        self.write_line_break()
+        leading_space = True
+        spaces = False
+        breaks = True
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if breaks:
+                if ch is None or ch not in '\n\x85\u2028\u2029':
+                    if not leading_space and ch is not None and ch != ' '   \
+                            and text[start] == '\n':
+                        self.write_line_break()
+                    leading_space = (ch == ' ')
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    if ch is not None:
+                        self.write_indent()
+                    start = end
+            elif spaces:
+                if ch != ' ':
+                    if start+1 == end and self.column > self.best_width:
+                        self.write_indent()
+                    else:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                    start = end
+            else:
+                if ch is None or ch in ' \n\x85\u2028\u2029':
+                    data = text[start:end]
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    if ch is None:
+                        self.write_line_break()
+                    start = end
+            if ch is not None:
+                breaks = (ch in '\n\x85\u2028\u2029')
+                spaces = (ch == ' ')
+            end += 1
+
+    def write_literal(self, text):
+        hints = self.determine_block_hints(text)
+        self.write_indicator('|'+hints, True)
+        if hints[-1:] == '+':
+            self.open_ended = True
+        self.write_line_break()
+        breaks = True
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if breaks:
+                if ch is None or ch not in '\n\x85\u2028\u2029':
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    if ch is not None:
+                        self.write_indent()
+                    start = end
+            else:
+                if ch is None or ch in '\n\x85\u2028\u2029':
+                    data = text[start:end]
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    if ch is None:
+                        self.write_line_break()
+                    start = end
+            if ch is not None:
+                breaks = (ch in '\n\x85\u2028\u2029')
+            end += 1
+
+    def write_plain(self, text, split=True):
+        if self.root_context:
+            self.open_ended = True
+        if not text:
+            return
+        if not self.whitespace:
+            data = ' '
+            self.column += len(data)
+            if self.encoding:
+                data = data.encode(self.encoding)
+            self.stream.write(data)
+        self.whitespace = False
+        self.indention = False
+        spaces = False
+        breaks = False
+        start = end = 0
+        while end <= len(text):
+            ch = None
+            if end < len(text):
+                ch = text[end]
+            if spaces:
+                if ch != ' ':
+                    if start+1 == end and self.column > self.best_width and split:
+                        self.write_indent()
+                        self.whitespace = False
+                        self.indention = False
+                    else:
+                        data = text[start:end]
+                        self.column += len(data)
+                        if self.encoding:
+                            data = data.encode(self.encoding)
+                        self.stream.write(data)
+                    start = end
+            elif breaks:
+                if ch not in '\n\x85\u2028\u2029':
+                    if text[start] == '\n':
+                        self.write_line_break()
+                    for br in text[start:end]:
+                        if br == '\n':
+                            self.write_line_break()
+                        else:
+                            self.write_line_break(br)
+                    self.write_indent()
+                    self.whitespace = False
+                    self.indention = False
+                    start = end
+            else:
+                if ch is None or ch in ' \n\x85\u2028\u2029':
+                    data = text[start:end]
+                    self.column += len(data)
+                    if self.encoding:
+                        data = data.encode(self.encoding)
+                    self.stream.write(data)
+                    start = end
+            if ch is not None:
+                spaces = (ch == ' ')
+                breaks = (ch in '\n\x85\u2028\u2029')
+            end += 1
diff --git a/libs/yaml/error.py b/libs/yaml/error.py
new file mode 100644
index 000000000..b796b4dc5
--- /dev/null
+++ b/libs/yaml/error.py
@@ -0,0 +1,75 @@
+
+__all__ = ['Mark', 'YAMLError', 'MarkedYAMLError']
+
+class Mark:
+
+    def __init__(self, name, index, line, column, buffer, pointer):
+        self.name = name
+        self.index = index
+        self.line = line
+        self.column = column
+        self.buffer = buffer
+        self.pointer = pointer
+
+    def get_snippet(self, indent=4, max_length=75):
+        if self.buffer is None:
+            return None
+        head = ''
+        start = self.pointer
+        while start > 0 and self.buffer[start-1] not in '\0\r\n\x85\u2028\u2029':
+            start -= 1
+            if self.pointer-start > max_length/2-1:
+                head = ' ... '
+                start += 5
+                break
+        tail = ''
+        end = self.pointer
+        while end < len(self.buffer) and self.buffer[end] not in '\0\r\n\x85\u2028\u2029':
+            end += 1
+            if end-self.pointer > max_length/2-1:
+                tail = ' ... '
+                end -= 5
+                break
+        snippet = self.buffer[start:end]
+        return ' '*indent + head + snippet + tail + '\n'  \
+                + ' '*(indent+self.pointer-start+len(head)) + '^'
+
+    def __str__(self):
+        snippet = self.get_snippet()
+        where = "  in \"%s\", line %d, column %d"   \
+                % (self.name, self.line+1, self.column+1)
+        if snippet is not None:
+            where += ":\n"+snippet
+        return where
+
+class YAMLError(Exception):
+    pass
+
+class MarkedYAMLError(YAMLError):
+
+    def __init__(self, context=None, context_mark=None,
+            problem=None, problem_mark=None, note=None):
+        self.context = context
+        self.context_mark = context_mark
+        self.problem = problem
+        self.problem_mark = problem_mark
+        self.note = note
+
+    def __str__(self):
+        lines = []
+        if self.context is not None:
+            lines.append(self.context)
+        if self.context_mark is not None  \
+            and (self.problem is None or self.problem_mark is None
+                    or self.context_mark.name != self.problem_mark.name
+                    or self.context_mark.line != self.problem_mark.line
+                    or self.context_mark.column != self.problem_mark.column):
+            lines.append(str(self.context_mark))
+        if self.problem is not None:
+            lines.append(self.problem)
+        if self.problem_mark is not None:
+            lines.append(str(self.problem_mark))
+        if self.note is not None:
+            lines.append(self.note)
+        return '\n'.join(lines)
+
diff --git a/libs/yaml/events.py b/libs/yaml/events.py
new file mode 100644
index 000000000..f79ad389c
--- /dev/null
+++ b/libs/yaml/events.py
@@ -0,0 +1,86 @@
+
+# Abstract classes.
+
+class Event(object):
+    def __init__(self, start_mark=None, end_mark=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+    def __repr__(self):
+        attributes = [key for key in ['anchor', 'tag', 'implicit', 'value']
+                if hasattr(self, key)]
+        arguments = ', '.join(['%s=%r' % (key, getattr(self, key))
+                for key in attributes])
+        return '%s(%s)' % (self.__class__.__name__, arguments)
+
+class NodeEvent(Event):
+    def __init__(self, anchor, start_mark=None, end_mark=None):
+        self.anchor = anchor
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class CollectionStartEvent(NodeEvent):
+    def __init__(self, anchor, tag, implicit, start_mark=None, end_mark=None,
+            flow_style=None):
+        self.anchor = anchor
+        self.tag = tag
+        self.implicit = implicit
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.flow_style = flow_style
+
+class CollectionEndEvent(Event):
+    pass
+
+# Implementations.
+
+class StreamStartEvent(Event):
+    def __init__(self, start_mark=None, end_mark=None, encoding=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.encoding = encoding
+
+class StreamEndEvent(Event):
+    pass
+
+class DocumentStartEvent(Event):
+    def __init__(self, start_mark=None, end_mark=None,
+            explicit=None, version=None, tags=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.explicit = explicit
+        self.version = version
+        self.tags = tags
+
+class DocumentEndEvent(Event):
+    def __init__(self, start_mark=None, end_mark=None,
+            explicit=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.explicit = explicit
+
+class AliasEvent(NodeEvent):
+    pass
+
+class ScalarEvent(NodeEvent):
+    def __init__(self, anchor, tag, implicit, value,
+            start_mark=None, end_mark=None, style=None):
+        self.anchor = anchor
+        self.tag = tag
+        self.implicit = implicit
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.style = style
+
+class SequenceStartEvent(CollectionStartEvent):
+    pass
+
+class SequenceEndEvent(CollectionEndEvent):
+    pass
+
+class MappingStartEvent(CollectionStartEvent):
+    pass
+
+class MappingEndEvent(CollectionEndEvent):
+    pass
+
diff --git a/libs/yaml/loader.py b/libs/yaml/loader.py
new file mode 100644
index 000000000..414cb2c15
--- /dev/null
+++ b/libs/yaml/loader.py
@@ -0,0 +1,63 @@
+
+__all__ = ['BaseLoader', 'FullLoader', 'SafeLoader', 'Loader', 'UnsafeLoader']
+
+from .reader import *
+from .scanner import *
+from .parser import *
+from .composer import *
+from .constructor import *
+from .resolver import *
+
+class BaseLoader(Reader, Scanner, Parser, Composer, BaseConstructor, BaseResolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        BaseConstructor.__init__(self)
+        BaseResolver.__init__(self)
+
+class FullLoader(Reader, Scanner, Parser, Composer, FullConstructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        FullConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class SafeLoader(Reader, Scanner, Parser, Composer, SafeConstructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        SafeConstructor.__init__(self)
+        Resolver.__init__(self)
+
+class Loader(Reader, Scanner, Parser, Composer, Constructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        Constructor.__init__(self)
+        Resolver.__init__(self)
+
+# UnsafeLoader is the same as Loader (which is and was always unsafe on
+# untrusted input). Use of either Loader or UnsafeLoader should be rare, since
+# FullLoad should be able to load almost all YAML safely. Loader is left intact
+# to ensure backwards compatability.
+class UnsafeLoader(Reader, Scanner, Parser, Composer, Constructor, Resolver):
+
+    def __init__(self, stream):
+        Reader.__init__(self, stream)
+        Scanner.__init__(self)
+        Parser.__init__(self)
+        Composer.__init__(self)
+        Constructor.__init__(self)
+        Resolver.__init__(self)
diff --git a/libs/yaml/nodes.py b/libs/yaml/nodes.py
new file mode 100644
index 000000000..c4f070c41
--- /dev/null
+++ b/libs/yaml/nodes.py
@@ -0,0 +1,49 @@
+
+class Node(object):
+    def __init__(self, tag, value, start_mark, end_mark):
+        self.tag = tag
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+    def __repr__(self):
+        value = self.value
+        #if isinstance(value, list):
+        #    if len(value) == 0:
+        #        value = '<empty>'
+        #    elif len(value) == 1:
+        #        value = '<1 item>'
+        #    else:
+        #        value = '<%d items>' % len(value)
+        #else:
+        #    if len(value) > 75:
+        #        value = repr(value[:70]+u' ... ')
+        #    else:
+        #        value = repr(value)
+        value = repr(value)
+        return '%s(tag=%r, value=%s)' % (self.__class__.__name__, self.tag, value)
+
+class ScalarNode(Node):
+    id = 'scalar'
+    def __init__(self, tag, value,
+            start_mark=None, end_mark=None, style=None):
+        self.tag = tag
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.style = style
+
+class CollectionNode(Node):
+    def __init__(self, tag, value,
+            start_mark=None, end_mark=None, flow_style=None):
+        self.tag = tag
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.flow_style = flow_style
+
+class SequenceNode(CollectionNode):
+    id = 'sequence'
+
+class MappingNode(CollectionNode):
+    id = 'mapping'
+
diff --git a/libs/yaml/parser.py b/libs/yaml/parser.py
new file mode 100644
index 000000000..13a5995d2
--- /dev/null
+++ b/libs/yaml/parser.py
@@ -0,0 +1,589 @@
+
+# The following YAML grammar is LL(1) and is parsed by a recursive descent
+# parser.
+#
+# stream            ::= STREAM-START implicit_document? explicit_document* STREAM-END
+# implicit_document ::= block_node DOCUMENT-END*
+# explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
+# block_node_or_indentless_sequence ::=
+#                       ALIAS
+#                       | properties (block_content | indentless_block_sequence)?
+#                       | block_content
+#                       | indentless_block_sequence
+# block_node        ::= ALIAS
+#                       | properties block_content?
+#                       | block_content
+# flow_node         ::= ALIAS
+#                       | properties flow_content?
+#                       | flow_content
+# properties        ::= TAG ANCHOR? | ANCHOR TAG?
+# block_content     ::= block_collection | flow_collection | SCALAR
+# flow_content      ::= flow_collection | SCALAR
+# block_collection  ::= block_sequence | block_mapping
+# flow_collection   ::= flow_sequence | flow_mapping
+# block_sequence    ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
+# indentless_sequence   ::= (BLOCK-ENTRY block_node?)+
+# block_mapping     ::= BLOCK-MAPPING_START
+#                       ((KEY block_node_or_indentless_sequence?)?
+#                       (VALUE block_node_or_indentless_sequence?)?)*
+#                       BLOCK-END
+# flow_sequence     ::= FLOW-SEQUENCE-START
+#                       (flow_sequence_entry FLOW-ENTRY)*
+#                       flow_sequence_entry?
+#                       FLOW-SEQUENCE-END
+# flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+# flow_mapping      ::= FLOW-MAPPING-START
+#                       (flow_mapping_entry FLOW-ENTRY)*
+#                       flow_mapping_entry?
+#                       FLOW-MAPPING-END
+# flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+#
+# FIRST sets:
+#
+# stream: { STREAM-START }
+# explicit_document: { DIRECTIVE DOCUMENT-START }
+# implicit_document: FIRST(block_node)
+# block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
+# flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
+# block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START }
+# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# block_sequence: { BLOCK-SEQUENCE-START }
+# block_mapping: { BLOCK-MAPPING-START }
+# block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY }
+# indentless_sequence: { ENTRY }
+# flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
+# flow_sequence: { FLOW-SEQUENCE-START }
+# flow_mapping: { FLOW-MAPPING-START }
+# flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
+# flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
+
+__all__ = ['Parser', 'ParserError']
+
+from .error import MarkedYAMLError
+from .tokens import *
+from .events import *
+from .scanner import *
+
+class ParserError(MarkedYAMLError):
+    pass
+
+class Parser:
+    # Since writing a recursive-descendant parser is a straightforward task, we
+    # do not give many comments here.
+
+    DEFAULT_TAGS = {
+        '!':   '!',
+        '!!':  'tag:yaml.org,2002:',
+    }
+
+    def __init__(self):
+        self.current_event = None
+        self.yaml_version = None
+        self.tag_handles = {}
+        self.states = []
+        self.marks = []
+        self.state = self.parse_stream_start
+
+    def dispose(self):
+        # Reset the state attributes (to clear self-references)
+        self.states = []
+        self.state = None
+
+    def check_event(self, *choices):
+        # Check the type of the next event.
+        if self.current_event is None:
+            if self.state:
+                self.current_event = self.state()
+        if self.current_event is not None:
+            if not choices:
+                return True
+            for choice in choices:
+                if isinstance(self.current_event, choice):
+                    return True
+        return False
+
+    def peek_event(self):
+        # Get the next event.
+        if self.current_event is None:
+            if self.state:
+                self.current_event = self.state()
+        return self.current_event
+
+    def get_event(self):
+        # Get the next event and proceed further.
+        if self.current_event is None:
+            if self.state:
+                self.current_event = self.state()
+        value = self.current_event
+        self.current_event = None
+        return value
+
+    # stream    ::= STREAM-START implicit_document? explicit_document* STREAM-END
+    # implicit_document ::= block_node DOCUMENT-END*
+    # explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
+
+    def parse_stream_start(self):
+
+        # Parse the stream start.
+        token = self.get_token()
+        event = StreamStartEvent(token.start_mark, token.end_mark,
+                encoding=token.encoding)
+
+        # Prepare the next state.
+        self.state = self.parse_implicit_document_start
+
+        return event
+
+    def parse_implicit_document_start(self):
+
+        # Parse an implicit document.
+        if not self.check_token(DirectiveToken, DocumentStartToken,
+                StreamEndToken):
+            self.tag_handles = self.DEFAULT_TAGS
+            token = self.peek_token()
+            start_mark = end_mark = token.start_mark
+            event = DocumentStartEvent(start_mark, end_mark,
+                    explicit=False)
+
+            # Prepare the next state.
+            self.states.append(self.parse_document_end)
+            self.state = self.parse_block_node
+
+            return event
+
+        else:
+            return self.parse_document_start()
+
+    def parse_document_start(self):
+
+        # Parse any extra document end indicators.
+        while self.check_token(DocumentEndToken):
+            self.get_token()
+
+        # Parse an explicit document.
+        if not self.check_token(StreamEndToken):
+            token = self.peek_token()
+            start_mark = token.start_mark
+            version, tags = self.process_directives()
+            if not self.check_token(DocumentStartToken):
+                raise ParserError(None, None,
+                        "expected '<document start>', but found %r"
+                        % self.peek_token().id,
+                        self.peek_token().start_mark)
+            token = self.get_token()
+            end_mark = token.end_mark
+            event = DocumentStartEvent(start_mark, end_mark,
+                    explicit=True, version=version, tags=tags)
+            self.states.append(self.parse_document_end)
+            self.state = self.parse_document_content
+        else:
+            # Parse the end of the stream.
+            token = self.get_token()
+            event = StreamEndEvent(token.start_mark, token.end_mark)
+            assert not self.states
+            assert not self.marks
+            self.state = None
+        return event
+
+    def parse_document_end(self):
+
+        # Parse the document end.
+        token = self.peek_token()
+        start_mark = end_mark = token.start_mark
+        explicit = False
+        if self.check_token(DocumentEndToken):
+            token = self.get_token()
+            end_mark = token.end_mark
+            explicit = True
+        event = DocumentEndEvent(start_mark, end_mark,
+                explicit=explicit)
+
+        # Prepare the next state.
+        self.state = self.parse_document_start
+
+        return event
+
+    def parse_document_content(self):
+        if self.check_token(DirectiveToken,
+                DocumentStartToken, DocumentEndToken, StreamEndToken):
+            event = self.process_empty_scalar(self.peek_token().start_mark)
+            self.state = self.states.pop()
+            return event
+        else:
+            return self.parse_block_node()
+
+    def process_directives(self):
+        self.yaml_version = None
+        self.tag_handles = {}
+        while self.check_token(DirectiveToken):
+            token = self.get_token()
+            if token.name == 'YAML':
+                if self.yaml_version is not None:
+                    raise ParserError(None, None,
+                            "found duplicate YAML directive", token.start_mark)
+                major, minor = token.value
+                if major != 1:
+                    raise ParserError(None, None,
+                            "found incompatible YAML document (version 1.* is required)",
+                            token.start_mark)
+                self.yaml_version = token.value
+            elif token.name == 'TAG':
+                handle, prefix = token.value
+                if handle in self.tag_handles:
+                    raise ParserError(None, None,
+                            "duplicate tag handle %r" % handle,
+                            token.start_mark)
+                self.tag_handles[handle] = prefix
+        if self.tag_handles:
+            value = self.yaml_version, self.tag_handles.copy()
+        else:
+            value = self.yaml_version, None
+        for key in self.DEFAULT_TAGS:
+            if key not in self.tag_handles:
+                self.tag_handles[key] = self.DEFAULT_TAGS[key]
+        return value
+
+    # block_node_or_indentless_sequence ::= ALIAS
+    #               | properties (block_content | indentless_block_sequence)?
+    #               | block_content
+    #               | indentless_block_sequence
+    # block_node    ::= ALIAS
+    #                   | properties block_content?
+    #                   | block_content
+    # flow_node     ::= ALIAS
+    #                   | properties flow_content?
+    #                   | flow_content
+    # properties    ::= TAG ANCHOR? | ANCHOR TAG?
+    # block_content     ::= block_collection | flow_collection | SCALAR
+    # flow_content      ::= flow_collection | SCALAR
+    # block_collection  ::= block_sequence | block_mapping
+    # flow_collection   ::= flow_sequence | flow_mapping
+
+    def parse_block_node(self):
+        return self.parse_node(block=True)
+
+    def parse_flow_node(self):
+        return self.parse_node()
+
+    def parse_block_node_or_indentless_sequence(self):
+        return self.parse_node(block=True, indentless_sequence=True)
+
+    def parse_node(self, block=False, indentless_sequence=False):
+        if self.check_token(AliasToken):
+            token = self.get_token()
+            event = AliasEvent(token.value, token.start_mark, token.end_mark)
+            self.state = self.states.pop()
+        else:
+            anchor = None
+            tag = None
+            start_mark = end_mark = tag_mark = None
+            if self.check_token(AnchorToken):
+                token = self.get_token()
+                start_mark = token.start_mark
+                end_mark = token.end_mark
+                anchor = token.value
+                if self.check_token(TagToken):
+                    token = self.get_token()
+                    tag_mark = token.start_mark
+                    end_mark = token.end_mark
+                    tag = token.value
+            elif self.check_token(TagToken):
+                token = self.get_token()
+                start_mark = tag_mark = token.start_mark
+                end_mark = token.end_mark
+                tag = token.value
+                if self.check_token(AnchorToken):
+                    token = self.get_token()
+                    end_mark = token.end_mark
+                    anchor = token.value
+            if tag is not None:
+                handle, suffix = tag
+                if handle is not None:
+                    if handle not in self.tag_handles:
+                        raise ParserError("while parsing a node", start_mark,
+                                "found undefined tag handle %r" % handle,
+                                tag_mark)
+                    tag = self.tag_handles[handle]+suffix
+                else:
+                    tag = suffix
+            #if tag == '!':
+            #    raise ParserError("while parsing a node", start_mark,
+            #            "found non-specific tag '!'", tag_mark,
+            #            "Please check 'http://pyyaml.org/wiki/YAMLNonSpecificTag' and share your opinion.")
+            if start_mark is None:
+                start_mark = end_mark = self.peek_token().start_mark
+            event = None
+            implicit = (tag is None or tag == '!')
+            if indentless_sequence and self.check_token(BlockEntryToken):
+                end_mark = self.peek_token().end_mark
+                event = SequenceStartEvent(anchor, tag, implicit,
+                        start_mark, end_mark)
+                self.state = self.parse_indentless_sequence_entry
+            else:
+                if self.check_token(ScalarToken):
+                    token = self.get_token()
+                    end_mark = token.end_mark
+                    if (token.plain and tag is None) or tag == '!':
+                        implicit = (True, False)
+                    elif tag is None:
+                        implicit = (False, True)
+                    else:
+                        implicit = (False, False)
+                    event = ScalarEvent(anchor, tag, implicit, token.value,
+                            start_mark, end_mark, style=token.style)
+                    self.state = self.states.pop()
+                elif self.check_token(FlowSequenceStartToken):
+                    end_mark = self.peek_token().end_mark
+                    event = SequenceStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=True)
+                    self.state = self.parse_flow_sequence_first_entry
+                elif self.check_token(FlowMappingStartToken):
+                    end_mark = self.peek_token().end_mark
+                    event = MappingStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=True)
+                    self.state = self.parse_flow_mapping_first_key
+                elif block and self.check_token(BlockSequenceStartToken):
+                    end_mark = self.peek_token().start_mark
+                    event = SequenceStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=False)
+                    self.state = self.parse_block_sequence_first_entry
+                elif block and self.check_token(BlockMappingStartToken):
+                    end_mark = self.peek_token().start_mark
+                    event = MappingStartEvent(anchor, tag, implicit,
+                            start_mark, end_mark, flow_style=False)
+                    self.state = self.parse_block_mapping_first_key
+                elif anchor is not None or tag is not None:
+                    # Empty scalars are allowed even if a tag or an anchor is
+                    # specified.
+                    event = ScalarEvent(anchor, tag, (implicit, False), '',
+                            start_mark, end_mark)
+                    self.state = self.states.pop()
+                else:
+                    if block:
+                        node = 'block'
+                    else:
+                        node = 'flow'
+                    token = self.peek_token()
+                    raise ParserError("while parsing a %s node" % node, start_mark,
+                            "expected the node content, but found %r" % token.id,
+                            token.start_mark)
+        return event
+
+    # block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
+
+    def parse_block_sequence_first_entry(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_block_sequence_entry()
+
+    def parse_block_sequence_entry(self):
+        if self.check_token(BlockEntryToken):
+            token = self.get_token()
+            if not self.check_token(BlockEntryToken, BlockEndToken):
+                self.states.append(self.parse_block_sequence_entry)
+                return self.parse_block_node()
+            else:
+                self.state = self.parse_block_sequence_entry
+                return self.process_empty_scalar(token.end_mark)
+        if not self.check_token(BlockEndToken):
+            token = self.peek_token()
+            raise ParserError("while parsing a block collection", self.marks[-1],
+                    "expected <block end>, but found %r" % token.id, token.start_mark)
+        token = self.get_token()
+        event = SequenceEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    # indentless_sequence ::= (BLOCK-ENTRY block_node?)+
+
+    def parse_indentless_sequence_entry(self):
+        if self.check_token(BlockEntryToken):
+            token = self.get_token()
+            if not self.check_token(BlockEntryToken,
+                    KeyToken, ValueToken, BlockEndToken):
+                self.states.append(self.parse_indentless_sequence_entry)
+                return self.parse_block_node()
+            else:
+                self.state = self.parse_indentless_sequence_entry
+                return self.process_empty_scalar(token.end_mark)
+        token = self.peek_token()
+        event = SequenceEndEvent(token.start_mark, token.start_mark)
+        self.state = self.states.pop()
+        return event
+
+    # block_mapping     ::= BLOCK-MAPPING_START
+    #                       ((KEY block_node_or_indentless_sequence?)?
+    #                       (VALUE block_node_or_indentless_sequence?)?)*
+    #                       BLOCK-END
+
+    def parse_block_mapping_first_key(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_block_mapping_key()
+
+    def parse_block_mapping_key(self):
+        if self.check_token(KeyToken):
+            token = self.get_token()
+            if not self.check_token(KeyToken, ValueToken, BlockEndToken):
+                self.states.append(self.parse_block_mapping_value)
+                return self.parse_block_node_or_indentless_sequence()
+            else:
+                self.state = self.parse_block_mapping_value
+                return self.process_empty_scalar(token.end_mark)
+        if not self.check_token(BlockEndToken):
+            token = self.peek_token()
+            raise ParserError("while parsing a block mapping", self.marks[-1],
+                    "expected <block end>, but found %r" % token.id, token.start_mark)
+        token = self.get_token()
+        event = MappingEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    def parse_block_mapping_value(self):
+        if self.check_token(ValueToken):
+            token = self.get_token()
+            if not self.check_token(KeyToken, ValueToken, BlockEndToken):
+                self.states.append(self.parse_block_mapping_key)
+                return self.parse_block_node_or_indentless_sequence()
+            else:
+                self.state = self.parse_block_mapping_key
+                return self.process_empty_scalar(token.end_mark)
+        else:
+            self.state = self.parse_block_mapping_key
+            token = self.peek_token()
+            return self.process_empty_scalar(token.start_mark)
+
+    # flow_sequence     ::= FLOW-SEQUENCE-START
+    #                       (flow_sequence_entry FLOW-ENTRY)*
+    #                       flow_sequence_entry?
+    #                       FLOW-SEQUENCE-END
+    # flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+    #
+    # Note that while production rules for both flow_sequence_entry and
+    # flow_mapping_entry are equal, their interpretations are different.
+    # For `flow_sequence_entry`, the part `KEY flow_node? (VALUE flow_node?)?`
+    # generate an inline mapping (set syntax).
+
+    def parse_flow_sequence_first_entry(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_flow_sequence_entry(first=True)
+
+    def parse_flow_sequence_entry(self, first=False):
+        if not self.check_token(FlowSequenceEndToken):
+            if not first:
+                if self.check_token(FlowEntryToken):
+                    self.get_token()
+                else:
+                    token = self.peek_token()
+                    raise ParserError("while parsing a flow sequence", self.marks[-1],
+                            "expected ',' or ']', but got %r" % token.id, token.start_mark)
+            
+            if self.check_token(KeyToken):
+                token = self.peek_token()
+                event = MappingStartEvent(None, None, True,
+                        token.start_mark, token.end_mark,
+                        flow_style=True)
+                self.state = self.parse_flow_sequence_entry_mapping_key
+                return event
+            elif not self.check_token(FlowSequenceEndToken):
+                self.states.append(self.parse_flow_sequence_entry)
+                return self.parse_flow_node()
+        token = self.get_token()
+        event = SequenceEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    def parse_flow_sequence_entry_mapping_key(self):
+        token = self.get_token()
+        if not self.check_token(ValueToken,
+                FlowEntryToken, FlowSequenceEndToken):
+            self.states.append(self.parse_flow_sequence_entry_mapping_value)
+            return self.parse_flow_node()
+        else:
+            self.state = self.parse_flow_sequence_entry_mapping_value
+            return self.process_empty_scalar(token.end_mark)
+
+    def parse_flow_sequence_entry_mapping_value(self):
+        if self.check_token(ValueToken):
+            token = self.get_token()
+            if not self.check_token(FlowEntryToken, FlowSequenceEndToken):
+                self.states.append(self.parse_flow_sequence_entry_mapping_end)
+                return self.parse_flow_node()
+            else:
+                self.state = self.parse_flow_sequence_entry_mapping_end
+                return self.process_empty_scalar(token.end_mark)
+        else:
+            self.state = self.parse_flow_sequence_entry_mapping_end
+            token = self.peek_token()
+            return self.process_empty_scalar(token.start_mark)
+
+    def parse_flow_sequence_entry_mapping_end(self):
+        self.state = self.parse_flow_sequence_entry
+        token = self.peek_token()
+        return MappingEndEvent(token.start_mark, token.start_mark)
+
+    # flow_mapping  ::= FLOW-MAPPING-START
+    #                   (flow_mapping_entry FLOW-ENTRY)*
+    #                   flow_mapping_entry?
+    #                   FLOW-MAPPING-END
+    # flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)?
+
+    def parse_flow_mapping_first_key(self):
+        token = self.get_token()
+        self.marks.append(token.start_mark)
+        return self.parse_flow_mapping_key(first=True)
+
+    def parse_flow_mapping_key(self, first=False):
+        if not self.check_token(FlowMappingEndToken):
+            if not first:
+                if self.check_token(FlowEntryToken):
+                    self.get_token()
+                else:
+                    token = self.peek_token()
+                    raise ParserError("while parsing a flow mapping", self.marks[-1],
+                            "expected ',' or '}', but got %r" % token.id, token.start_mark)
+            if self.check_token(KeyToken):
+                token = self.get_token()
+                if not self.check_token(ValueToken,
+                        FlowEntryToken, FlowMappingEndToken):
+                    self.states.append(self.parse_flow_mapping_value)
+                    return self.parse_flow_node()
+                else:
+                    self.state = self.parse_flow_mapping_value
+                    return self.process_empty_scalar(token.end_mark)
+            elif not self.check_token(FlowMappingEndToken):
+                self.states.append(self.parse_flow_mapping_empty_value)
+                return self.parse_flow_node()
+        token = self.get_token()
+        event = MappingEndEvent(token.start_mark, token.end_mark)
+        self.state = self.states.pop()
+        self.marks.pop()
+        return event
+
+    def parse_flow_mapping_value(self):
+        if self.check_token(ValueToken):
+            token = self.get_token()
+            if not self.check_token(FlowEntryToken, FlowMappingEndToken):
+                self.states.append(self.parse_flow_mapping_key)
+                return self.parse_flow_node()
+            else:
+                self.state = self.parse_flow_mapping_key
+                return self.process_empty_scalar(token.end_mark)
+        else:
+            self.state = self.parse_flow_mapping_key
+            token = self.peek_token()
+            return self.process_empty_scalar(token.start_mark)
+
+    def parse_flow_mapping_empty_value(self):
+        self.state = self.parse_flow_mapping_key
+        return self.process_empty_scalar(self.peek_token().start_mark)
+
+    def process_empty_scalar(self, mark):
+        return ScalarEvent(None, None, (True, False), '', mark, mark)
+
diff --git a/libs/yaml/reader.py b/libs/yaml/reader.py
new file mode 100644
index 000000000..774b0219b
--- /dev/null
+++ b/libs/yaml/reader.py
@@ -0,0 +1,185 @@
+# This module contains abstractions for the input stream. You don't have to
+# looks further, there are no pretty code.
+#
+# We define two classes here.
+#
+#   Mark(source, line, column)
+# It's just a record and its only use is producing nice error messages.
+# Parser does not use it for any other purposes.
+#
+#   Reader(source, data)
+# Reader determines the encoding of `data` and converts it to unicode.
+# Reader provides the following methods and attributes:
+#   reader.peek(length=1) - return the next `length` characters
+#   reader.forward(length=1) - move the current position to `length` characters.
+#   reader.index - the number of the current character.
+#   reader.line, stream.column - the line and the column of the current character.
+
+__all__ = ['Reader', 'ReaderError']
+
+from .error import YAMLError, Mark
+
+import codecs, re
+
+class ReaderError(YAMLError):
+
+    def __init__(self, name, position, character, encoding, reason):
+        self.name = name
+        self.character = character
+        self.position = position
+        self.encoding = encoding
+        self.reason = reason
+
+    def __str__(self):
+        if isinstance(self.character, bytes):
+            return "'%s' codec can't decode byte #x%02x: %s\n"  \
+                    "  in \"%s\", position %d"    \
+                    % (self.encoding, ord(self.character), self.reason,
+                            self.name, self.position)
+        else:
+            return "unacceptable character #x%04x: %s\n"    \
+                    "  in \"%s\", position %d"    \
+                    % (self.character, self.reason,
+                            self.name, self.position)
+
+class Reader(object):
+    # Reader:
+    # - determines the data encoding and converts it to a unicode string,
+    # - checks if characters are in allowed range,
+    # - adds '\0' to the end.
+
+    # Reader accepts
+    #  - a `bytes` object,
+    #  - a `str` object,
+    #  - a file-like object with its `read` method returning `str`,
+    #  - a file-like object with its `read` method returning `unicode`.
+
+    # Yeah, it's ugly and slow.
+
+    def __init__(self, stream):
+        self.name = None
+        self.stream = None
+        self.stream_pointer = 0
+        self.eof = True
+        self.buffer = ''
+        self.pointer = 0
+        self.raw_buffer = None
+        self.raw_decode = None
+        self.encoding = None
+        self.index = 0
+        self.line = 0
+        self.column = 0
+        if isinstance(stream, str):
+            self.name = "<unicode string>"
+            self.check_printable(stream)
+            self.buffer = stream+'\0'
+        elif isinstance(stream, bytes):
+            self.name = "<byte string>"
+            self.raw_buffer = stream
+            self.determine_encoding()
+        else:
+            self.stream = stream
+            self.name = getattr(stream, 'name', "<file>")
+            self.eof = False
+            self.raw_buffer = None
+            self.determine_encoding()
+
+    def peek(self, index=0):
+        try:
+            return self.buffer[self.pointer+index]
+        except IndexError:
+            self.update(index+1)
+            return self.buffer[self.pointer+index]
+
+    def prefix(self, length=1):
+        if self.pointer+length >= len(self.buffer):
+            self.update(length)
+        return self.buffer[self.pointer:self.pointer+length]
+
+    def forward(self, length=1):
+        if self.pointer+length+1 >= len(self.buffer):
+            self.update(length+1)
+        while length:
+            ch = self.buffer[self.pointer]
+            self.pointer += 1
+            self.index += 1
+            if ch in '\n\x85\u2028\u2029'  \
+                    or (ch == '\r' and self.buffer[self.pointer] != '\n'):
+                self.line += 1
+                self.column = 0
+            elif ch != '\uFEFF':
+                self.column += 1
+            length -= 1
+
+    def get_mark(self):
+        if self.stream is None:
+            return Mark(self.name, self.index, self.line, self.column,
+                    self.buffer, self.pointer)
+        else:
+            return Mark(self.name, self.index, self.line, self.column,
+                    None, None)
+
+    def determine_encoding(self):
+        while not self.eof and (self.raw_buffer is None or len(self.raw_buffer) < 2):
+            self.update_raw()
+        if isinstance(self.raw_buffer, bytes):
+            if self.raw_buffer.startswith(codecs.BOM_UTF16_LE):
+                self.raw_decode = codecs.utf_16_le_decode
+                self.encoding = 'utf-16-le'
+            elif self.raw_buffer.startswith(codecs.BOM_UTF16_BE):
+                self.raw_decode = codecs.utf_16_be_decode
+                self.encoding = 'utf-16-be'
+            else:
+                self.raw_decode = codecs.utf_8_decode
+                self.encoding = 'utf-8'
+        self.update(1)
+
+    NON_PRINTABLE = re.compile('[^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uD7FF\uE000-\uFFFD\U00010000-\U0010ffff]')
+    def check_printable(self, data):
+        match = self.NON_PRINTABLE.search(data)
+        if match:
+            character = match.group()
+            position = self.index+(len(self.buffer)-self.pointer)+match.start()
+            raise ReaderError(self.name, position, ord(character),
+                    'unicode', "special characters are not allowed")
+
+    def update(self, length):
+        if self.raw_buffer is None:
+            return
+        self.buffer = self.buffer[self.pointer:]
+        self.pointer = 0
+        while len(self.buffer) < length:
+            if not self.eof:
+                self.update_raw()
+            if self.raw_decode is not None:
+                try:
+                    data, converted = self.raw_decode(self.raw_buffer,
+                            'strict', self.eof)
+                except UnicodeDecodeError as exc:
+                    character = self.raw_buffer[exc.start]
+                    if self.stream is not None:
+                        position = self.stream_pointer-len(self.raw_buffer)+exc.start
+                    else:
+                        position = exc.start
+                    raise ReaderError(self.name, position, character,
+                            exc.encoding, exc.reason)
+            else:
+                data = self.raw_buffer
+                converted = len(data)
+            self.check_printable(data)
+            self.buffer += data
+            self.raw_buffer = self.raw_buffer[converted:]
+            if self.eof:
+                self.buffer += '\0'
+                self.raw_buffer = None
+                break
+
+    def update_raw(self, size=4096):
+        data = self.stream.read(size)
+        if self.raw_buffer is None:
+            self.raw_buffer = data
+        else:
+            self.raw_buffer += data
+        self.stream_pointer += len(data)
+        if not data:
+            self.eof = True
diff --git a/libs/yaml/representer.py b/libs/yaml/representer.py
new file mode 100644
index 000000000..dd144017b
--- /dev/null
+++ b/libs/yaml/representer.py
@@ -0,0 +1,389 @@
+
+__all__ = ['BaseRepresenter', 'SafeRepresenter', 'Representer',
+    'RepresenterError']
+
+from .error import *
+from .nodes import *
+
+import datetime, sys, copyreg, types, base64, collections
+
+class RepresenterError(YAMLError):
+    pass
+
+class BaseRepresenter:
+
+    yaml_representers = {}
+    yaml_multi_representers = {}
+
+    def __init__(self, default_style=None, default_flow_style=False, sort_keys=True):
+        self.default_style = default_style
+        self.sort_keys = sort_keys
+        self.default_flow_style = default_flow_style
+        self.represented_objects = {}
+        self.object_keeper = []
+        self.alias_key = None
+
+    def represent(self, data):
+        node = self.represent_data(data)
+        self.serialize(node)
+        self.represented_objects = {}
+        self.object_keeper = []
+        self.alias_key = None
+
+    def represent_data(self, data):
+        if self.ignore_aliases(data):
+            self.alias_key = None
+        else:
+            self.alias_key = id(data)
+        if self.alias_key is not None:
+            if self.alias_key in self.represented_objects:
+                node = self.represented_objects[self.alias_key]
+                #if node is None:
+                #    raise RepresenterError("recursive objects are not allowed: %r" % data)
+                return node
+            #self.represented_objects[alias_key] = None
+            self.object_keeper.append(data)
+        data_types = type(data).__mro__
+        if data_types[0] in self.yaml_representers:
+            node = self.yaml_representers[data_types[0]](self, data)
+        else:
+            for data_type in data_types:
+                if data_type in self.yaml_multi_representers:
+                    node = self.yaml_multi_representers[data_type](self, data)
+                    break
+            else:
+                if None in self.yaml_multi_representers:
+                    node = self.yaml_multi_representers[None](self, data)
+                elif None in self.yaml_representers:
+                    node = self.yaml_representers[None](self, data)
+                else:
+                    node = ScalarNode(None, str(data))
+        #if alias_key is not None:
+        #    self.represented_objects[alias_key] = node
+        return node
+
+    @classmethod
+    def add_representer(cls, data_type, representer):
+        if not 'yaml_representers' in cls.__dict__:
+            cls.yaml_representers = cls.yaml_representers.copy()
+        cls.yaml_representers[data_type] = representer
+
+    @classmethod
+    def add_multi_representer(cls, data_type, representer):
+        if not 'yaml_multi_representers' in cls.__dict__:
+            cls.yaml_multi_representers = cls.yaml_multi_representers.copy()
+        cls.yaml_multi_representers[data_type] = representer
+
+    def represent_scalar(self, tag, value, style=None):
+        if style is None:
+            style = self.default_style
+        node = ScalarNode(tag, value, style=style)
+        if self.alias_key is not None:
+            self.represented_objects[self.alias_key] = node
+        return node
+
+    def represent_sequence(self, tag, sequence, flow_style=None):
+        value = []
+        node = SequenceNode(tag, value, flow_style=flow_style)
+        if self.alias_key is not None:
+            self.represented_objects[self.alias_key] = node
+        best_style = True
+        for item in sequence:
+            node_item = self.represent_data(item)
+            if not (isinstance(node_item, ScalarNode) and not node_item.style):
+                best_style = False
+            value.append(node_item)
+        if flow_style is None:
+            if self.default_flow_style is not None:
+                node.flow_style = self.default_flow_style
+            else:
+                node.flow_style = best_style
+        return node
+
+    def represent_mapping(self, tag, mapping, flow_style=None):
+        value = []
+        node = MappingNode(tag, value, flow_style=flow_style)
+        if self.alias_key is not None:
+            self.represented_objects[self.alias_key] = node
+        best_style = True
+        if hasattr(mapping, 'items'):
+            mapping = list(mapping.items())
+            if self.sort_keys:
+                try:
+                    mapping = sorted(mapping)
+                except TypeError:
+                    pass
+        for item_key, item_value in mapping:
+            node_key = self.represent_data(item_key)
+            node_value = self.represent_data(item_value)
+            if not (isinstance(node_key, ScalarNode) and not node_key.style):
+                best_style = False
+            if not (isinstance(node_value, ScalarNode) and not node_value.style):
+                best_style = False
+            value.append((node_key, node_value))
+        if flow_style is None:
+            if self.default_flow_style is not None:
+                node.flow_style = self.default_flow_style
+            else:
+                node.flow_style = best_style
+        return node
+
+    def ignore_aliases(self, data):
+        return False
+
+class SafeRepresenter(BaseRepresenter):
+
+    def ignore_aliases(self, data):
+        if data is None:
+            return True
+        if isinstance(data, tuple) and data == ():
+            return True
+        if isinstance(data, (str, bytes, bool, int, float)):
+            return True
+
+    def represent_none(self, data):
+        return self.represent_scalar('tag:yaml.org,2002:null', 'null')
+
+    def represent_str(self, data):
+        return self.represent_scalar('tag:yaml.org,2002:str', data)
+
+    def represent_binary(self, data):
+        if hasattr(base64, 'encodebytes'):
+            data = base64.encodebytes(data).decode('ascii')
+        else:
+            data = base64.encodestring(data).decode('ascii')
+        return self.represent_scalar('tag:yaml.org,2002:binary', data, style='|')
+
+    def represent_bool(self, data):
+        if data:
+            value = 'true'
+        else:
+            value = 'false'
+        return self.represent_scalar('tag:yaml.org,2002:bool', value)
+
+    def represent_int(self, data):
+        return self.represent_scalar('tag:yaml.org,2002:int', str(data))
+
+    inf_value = 1e300
+    while repr(inf_value) != repr(inf_value*inf_value):
+        inf_value *= inf_value
+
+    def represent_float(self, data):
+        if data != data or (data == 0.0 and data == 1.0):
+            value = '.nan'
+        elif data == self.inf_value:
+            value = '.inf'
+        elif data == -self.inf_value:
+            value = '-.inf'
+        else:
+            value = repr(data).lower()
+            # Note that in some cases `repr(data)` represents a float number
+            # without the decimal parts.  For instance:
+            #   >>> repr(1e17)
+            #   '1e17'
+            # Unfortunately, this is not a valid float representation according
+            # to the definition of the `!!float` tag.  We fix this by adding
+            # '.0' before the 'e' symbol.
+            if '.' not in value and 'e' in value:
+                value = value.replace('e', '.0e', 1)
+        return self.represent_scalar('tag:yaml.org,2002:float', value)
+
+    def represent_list(self, data):
+        #pairs = (len(data) > 0 and isinstance(data, list))
+        #if pairs:
+        #    for item in data:
+        #        if not isinstance(item, tuple) or len(item) != 2:
+        #            pairs = False
+        #            break
+        #if not pairs:
+            return self.represent_sequence('tag:yaml.org,2002:seq', data)
+        #value = []
+        #for item_key, item_value in data:
+        #    value.append(self.represent_mapping(u'tag:yaml.org,2002:map',
+        #        [(item_key, item_value)]))
+        #return SequenceNode(u'tag:yaml.org,2002:pairs', value)
+
+    def represent_dict(self, data):
+        return self.represent_mapping('tag:yaml.org,2002:map', data)
+
+    def represent_set(self, data):
+        value = {}
+        for key in data:
+            value[key] = None
+        return self.represent_mapping('tag:yaml.org,2002:set', value)
+
+    def represent_date(self, data):
+        value = data.isoformat()
+        return self.represent_scalar('tag:yaml.org,2002:timestamp', value)
+
+    def represent_datetime(self, data):
+        value = data.isoformat(' ')
+        return self.represent_scalar('tag:yaml.org,2002:timestamp', value)
+
+    def represent_yaml_object(self, tag, data, cls, flow_style=None):
+        if hasattr(data, '__getstate__'):
+            state = data.__getstate__()
+        else:
+            state = data.__dict__.copy()
+        return self.represent_mapping(tag, state, flow_style=flow_style)
+
+    def represent_undefined(self, data):
+        raise RepresenterError("cannot represent an object", data)
+
+SafeRepresenter.add_representer(type(None),
+        SafeRepresenter.represent_none)
+
+SafeRepresenter.add_representer(str,
+        SafeRepresenter.represent_str)
+
+SafeRepresenter.add_representer(bytes,
+        SafeRepresenter.represent_binary)
+
+SafeRepresenter.add_representer(bool,
+        SafeRepresenter.represent_bool)
+
+SafeRepresenter.add_representer(int,
+        SafeRepresenter.represent_int)
+
+SafeRepresenter.add_representer(float,
+        SafeRepresenter.represent_float)
+
+SafeRepresenter.add_representer(list,
+        SafeRepresenter.represent_list)
+
+SafeRepresenter.add_representer(tuple,
+        SafeRepresenter.represent_list)
+
+SafeRepresenter.add_representer(dict,
+        SafeRepresenter.represent_dict)
+
+SafeRepresenter.add_representer(set,
+        SafeRepresenter.represent_set)
+
+SafeRepresenter.add_representer(datetime.date,
+        SafeRepresenter.represent_date)
+
+SafeRepresenter.add_representer(datetime.datetime,
+        SafeRepresenter.represent_datetime)
+
+SafeRepresenter.add_representer(None,
+        SafeRepresenter.represent_undefined)
+
+class Representer(SafeRepresenter):
+
+    def represent_complex(self, data):
+        if data.imag == 0.0:
+            data = '%r' % data.real
+        elif data.real == 0.0:
+            data = '%rj' % data.imag
+        elif data.imag > 0:
+            data = '%r+%rj' % (data.real, data.imag)
+        else:
+            data = '%r%rj' % (data.real, data.imag)
+        return self.represent_scalar('tag:yaml.org,2002:python/complex', data)
+
+    def represent_tuple(self, data):
+        return self.represent_sequence('tag:yaml.org,2002:python/tuple', data)
+
+    def represent_name(self, data):
+        name = '%s.%s' % (data.__module__, data.__name__)
+        return self.represent_scalar('tag:yaml.org,2002:python/name:'+name, '')
+
+    def represent_module(self, data):
+        return self.represent_scalar(
+                'tag:yaml.org,2002:python/module:'+data.__name__, '')
+
+    def represent_object(self, data):
+        # We use __reduce__ API to save the data. data.__reduce__ returns
+        # a tuple of length 2-5:
+        #   (function, args, state, listitems, dictitems)
+
+        # For reconstructing, we calls function(*args), then set its state,
+        # listitems, and dictitems if they are not None.
+
+        # A special case is when function.__name__ == '__newobj__'. In this
+        # case we create the object with args[0].__new__(*args).
+
+        # Another special case is when __reduce__ returns a string - we don't
+        # support it.
+
+        # We produce a !!python/object, !!python/object/new or
+        # !!python/object/apply node.
+
+        cls = type(data)
+        if cls in copyreg.dispatch_table:
+            reduce = copyreg.dispatch_table[cls](data)
+        elif hasattr(data, '__reduce_ex__'):
+            reduce = data.__reduce_ex__(2)
+        elif hasattr(data, '__reduce__'):
+            reduce = data.__reduce__()
+        else:
+            raise RepresenterError("cannot represent an object", data)
+        reduce = (list(reduce)+[None]*5)[:5]
+        function, args, state, listitems, dictitems = reduce
+        args = list(args)
+        if state is None:
+            state = {}
+        if listitems is not None:
+            listitems = list(listitems)
+        if dictitems is not None:
+            dictitems = dict(dictitems)
+        if function.__name__ == '__newobj__':
+            function = args[0]
+            args = args[1:]
+            tag = 'tag:yaml.org,2002:python/object/new:'
+            newobj = True
+        else:
+            tag = 'tag:yaml.org,2002:python/object/apply:'
+            newobj = False
+        function_name = '%s.%s' % (function.__module__, function.__name__)
+        if not args and not listitems and not dictitems \
+                and isinstance(state, dict) and newobj:
+            return self.represent_mapping(
+                    'tag:yaml.org,2002:python/object:'+function_name, state)
+        if not listitems and not dictitems  \
+                and isinstance(state, dict) and not state:
+            return self.represent_sequence(tag+function_name, args)
+        value = {}
+        if args:
+            value['args'] = args
+        if state or not isinstance(state, dict):
+            value['state'] = state
+        if listitems:
+            value['listitems'] = listitems
+        if dictitems:
+            value['dictitems'] = dictitems
+        return self.represent_mapping(tag+function_name, value)
+
+    def represent_ordered_dict(self, data):
+        # Provide uniform representation across different Python versions.
+        data_type = type(data)
+        tag = 'tag:yaml.org,2002:python/object/apply:%s.%s' \
+                % (data_type.__module__, data_type.__name__)
+        items = [[key, value] for key, value in data.items()]
+        return self.represent_sequence(tag, [items])
+
+Representer.add_representer(complex,
+        Representer.represent_complex)
+
+Representer.add_representer(tuple,
+        Representer.represent_tuple)
+
+Representer.add_representer(type,
+        Representer.represent_name)
+
+Representer.add_representer(collections.OrderedDict,
+        Representer.represent_ordered_dict)
+
+Representer.add_representer(types.FunctionType,
+        Representer.represent_name)
+
+Representer.add_representer(types.BuiltinFunctionType,
+        Representer.represent_name)
+
+Representer.add_representer(types.ModuleType,
+        Representer.represent_module)
+
+Representer.add_multi_representer(object,
+        Representer.represent_object)
+
diff --git a/libs/yaml/resolver.py b/libs/yaml/resolver.py
new file mode 100644
index 000000000..02b82e73e
--- /dev/null
+++ b/libs/yaml/resolver.py
@@ -0,0 +1,227 @@
+
+__all__ = ['BaseResolver', 'Resolver']
+
+from .error import *
+from .nodes import *
+
+import re
+
+class ResolverError(YAMLError):
+    pass
+
+class BaseResolver:
+
+    DEFAULT_SCALAR_TAG = 'tag:yaml.org,2002:str'
+    DEFAULT_SEQUENCE_TAG = 'tag:yaml.org,2002:seq'
+    DEFAULT_MAPPING_TAG = 'tag:yaml.org,2002:map'
+
+    yaml_implicit_resolvers = {}
+    yaml_path_resolvers = {}
+
+    def __init__(self):
+        self.resolver_exact_paths = []
+        self.resolver_prefix_paths = []
+
+    @classmethod
+    def add_implicit_resolver(cls, tag, regexp, first):
+        if not 'yaml_implicit_resolvers' in cls.__dict__:
+            implicit_resolvers = {}
+            for key in cls.yaml_implicit_resolvers:
+                implicit_resolvers[key] = cls.yaml_implicit_resolvers[key][:]
+            cls.yaml_implicit_resolvers = implicit_resolvers
+        if first is None:
+            first = [None]
+        for ch in first:
+            cls.yaml_implicit_resolvers.setdefault(ch, []).append((tag, regexp))
+
+    @classmethod
+    def add_path_resolver(cls, tag, path, kind=None):
+        # Note: `add_path_resolver` is experimental.  The API could be changed.
+        # `new_path` is a pattern that is matched against the path from the
+        # root to the node that is being considered.  `node_path` elements are
+        # tuples `(node_check, index_check)`.  `node_check` is a node class:
+        # `ScalarNode`, `SequenceNode`, `MappingNode` or `None`.  `None`
+        # matches any kind of a node.  `index_check` could be `None`, a boolean
+        # value, a string value, or a number.  `None` and `False` match against
+        # any _value_ of sequence and mapping nodes.  `True` matches against
+        # any _key_ of a mapping node.  A string `index_check` matches against
+        # a mapping value that corresponds to a scalar key which content is
+        # equal to the `index_check` value.  An integer `index_check` matches
+        # against a sequence value with the index equal to `index_check`.
+        if not 'yaml_path_resolvers' in cls.__dict__:
+            cls.yaml_path_resolvers = cls.yaml_path_resolvers.copy()
+        new_path = []
+        for element in path:
+            if isinstance(element, (list, tuple)):
+                if len(element) == 2:
+                    node_check, index_check = element
+                elif len(element) == 1:
+                    node_check = element[0]
+                    index_check = True
+                else:
+                    raise ResolverError("Invalid path element: %s" % element)
+            else:
+                node_check = None
+                index_check = element
+            if node_check is str:
+                node_check = ScalarNode
+            elif node_check is list:
+                node_check = SequenceNode
+            elif node_check is dict:
+                node_check = MappingNode
+            elif node_check not in [ScalarNode, SequenceNode, MappingNode]  \
+                    and not isinstance(node_check, str) \
+                    and node_check is not None:
+                raise ResolverError("Invalid node checker: %s" % node_check)
+            if not isinstance(index_check, (str, int))  \
+                    and index_check is not None:
+                raise ResolverError("Invalid index checker: %s" % index_check)
+            new_path.append((node_check, index_check))
+        if kind is str:
+            kind = ScalarNode
+        elif kind is list:
+            kind = SequenceNode
+        elif kind is dict:
+            kind = MappingNode
+        elif kind not in [ScalarNode, SequenceNode, MappingNode]    \
+                and kind is not None:
+            raise ResolverError("Invalid node kind: %s" % kind)
+        cls.yaml_path_resolvers[tuple(new_path), kind] = tag
+
+    def descend_resolver(self, current_node, current_index):
+        if not self.yaml_path_resolvers:
+            return
+        exact_paths = {}
+        prefix_paths = []
+        if current_node:
+            depth = len(self.resolver_prefix_paths)
+            for path, kind in self.resolver_prefix_paths[-1]:
+                if self.check_resolver_prefix(depth, path, kind,
+                        current_node, current_index):
+                    if len(path) > depth:
+                        prefix_paths.append((path, kind))
+                    else:
+                        exact_paths[kind] = self.yaml_path_resolvers[path, kind]
+        else:
+            for path, kind in self.yaml_path_resolvers:
+                if not path:
+                    exact_paths[kind] = self.yaml_path_resolvers[path, kind]
+                else:
+                    prefix_paths.append((path, kind))
+        self.resolver_exact_paths.append(exact_paths)
+        self.resolver_prefix_paths.append(prefix_paths)
+
+    def ascend_resolver(self):
+        if not self.yaml_path_resolvers:
+            return
+        self.resolver_exact_paths.pop()
+        self.resolver_prefix_paths.pop()
+
+    def check_resolver_prefix(self, depth, path, kind,
+            current_node, current_index):
+        node_check, index_check = path[depth-1]
+        if isinstance(node_check, str):
+            if current_node.tag != node_check:
+                return
+        elif node_check is not None:
+            if not isinstance(current_node, node_check):
+                return
+        if index_check is True and current_index is not None:
+            return
+        if (index_check is False or index_check is None)    \
+                and current_index is None:
+            return
+        if isinstance(index_check, str):
+            if not (isinstance(current_index, ScalarNode)
+                    and index_check == current_index.value):
+                return
+        elif isinstance(index_check, int) and not isinstance(index_check, bool):
+            if index_check != current_index:
+                return
+        return True
+
+    def resolve(self, kind, value, implicit):
+        if kind is ScalarNode and implicit[0]:
+            if value == '':
+                resolvers = self.yaml_implicit_resolvers.get('', [])
+            else:
+                resolvers = self.yaml_implicit_resolvers.get(value[0], [])
+            resolvers += self.yaml_implicit_resolvers.get(None, [])
+            for tag, regexp in resolvers:
+                if regexp.match(value):
+                    return tag
+            implicit = implicit[1]
+        if self.yaml_path_resolvers:
+            exact_paths = self.resolver_exact_paths[-1]
+            if kind in exact_paths:
+                return exact_paths[kind]
+            if None in exact_paths:
+                return exact_paths[None]
+        if kind is ScalarNode:
+            return self.DEFAULT_SCALAR_TAG
+        elif kind is SequenceNode:
+            return self.DEFAULT_SEQUENCE_TAG
+        elif kind is MappingNode:
+            return self.DEFAULT_MAPPING_TAG
+
+class Resolver(BaseResolver):
+    pass
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:bool',
+        re.compile(r'''^(?:yes|Yes|YES|no|No|NO
+                    |true|True|TRUE|false|False|FALSE
+                    |on|On|ON|off|Off|OFF)$''', re.X),
+        list('yYnNtTfFoO'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:float',
+        re.compile(r'''^(?:[-+]?(?:[0-9][0-9_]*)\.[0-9_]*(?:[eE][-+][0-9]+)?
+                    |\.[0-9_]+(?:[eE][-+][0-9]+)?
+                    |[-+]?[0-9][0-9_]*(?::[0-5]?[0-9])+\.[0-9_]*
+                    |[-+]?\.(?:inf|Inf|INF)
+                    |\.(?:nan|NaN|NAN))$''', re.X),
+        list('-+0123456789.'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:int',
+        re.compile(r'''^(?:[-+]?0b[0-1_]+
+                    |[-+]?0[0-7_]+
+                    |[-+]?(?:0|[1-9][0-9_]*)
+                    |[-+]?0x[0-9a-fA-F_]+
+                    |[-+]?[1-9][0-9_]*(?::[0-5]?[0-9])+)$''', re.X),
+        list('-+0123456789'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:merge',
+        re.compile(r'^(?:<<)$'),
+        ['<'])
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:null',
+        re.compile(r'''^(?: ~
+                    |null|Null|NULL
+                    | )$''', re.X),
+        ['~', 'n', 'N', ''])
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:timestamp',
+        re.compile(r'''^(?:[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]
+                    |[0-9][0-9][0-9][0-9] -[0-9][0-9]? -[0-9][0-9]?
+                     (?:[Tt]|[ \t]+)[0-9][0-9]?
+                     :[0-9][0-9] :[0-9][0-9] (?:\.[0-9]*)?
+                     (?:[ \t]*(?:Z|[-+][0-9][0-9]?(?::[0-9][0-9])?))?)$''', re.X),
+        list('0123456789'))
+
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:value',
+        re.compile(r'^(?:=)$'),
+        ['='])
+
+# The following resolver is only for documentation purposes. It cannot work
+# because plain scalars cannot start with '!', '&', or '*'.
+Resolver.add_implicit_resolver(
+        'tag:yaml.org,2002:yaml',
+        re.compile(r'^(?:!|&|\*)$'),
+        list('!&*'))
+
diff --git a/libs/yaml/scanner.py b/libs/yaml/scanner.py
new file mode 100644
index 000000000..775dbcc6d
--- /dev/null
+++ b/libs/yaml/scanner.py
@@ -0,0 +1,1435 @@
+
+# Scanner produces tokens of the following types:
+# STREAM-START
+# STREAM-END
+# DIRECTIVE(name, value)
+# DOCUMENT-START
+# DOCUMENT-END
+# BLOCK-SEQUENCE-START
+# BLOCK-MAPPING-START
+# BLOCK-END
+# FLOW-SEQUENCE-START
+# FLOW-MAPPING-START
+# FLOW-SEQUENCE-END
+# FLOW-MAPPING-END
+# BLOCK-ENTRY
+# FLOW-ENTRY
+# KEY
+# VALUE
+# ALIAS(value)
+# ANCHOR(value)
+# TAG(value)
+# SCALAR(value, plain, style)
+#
+# Read comments in the Scanner code for more details.
+#
+
+__all__ = ['Scanner', 'ScannerError']
+
+from .error import MarkedYAMLError
+from .tokens import *
+
+class ScannerError(MarkedYAMLError):
+    pass
+
+class SimpleKey:
+    # See below simple keys treatment.
+
+    def __init__(self, token_number, required, index, line, column, mark):
+        self.token_number = token_number
+        self.required = required
+        self.index = index
+        self.line = line
+        self.column = column
+        self.mark = mark
+
+class Scanner:
+
+    def __init__(self):
+        """Initialize the scanner."""
+        # It is assumed that Scanner and Reader will have a common descendant.
+        # Reader do the dirty work of checking for BOM and converting the
+        # input data to Unicode. It also adds NUL to the end.
+        #
+        # Reader supports the following methods
+        #   self.peek(i=0)       # peek the next i-th character
+        #   self.prefix(l=1)     # peek the next l characters
+        #   self.forward(l=1)    # read the next l characters and move the pointer.
+
+        # Had we reached the end of the stream?
+        self.done = False
+
+        # The number of unclosed '{' and '['. `flow_level == 0` means block
+        # context.
+        self.flow_level = 0
+
+        # List of processed tokens that are not yet emitted.
+        self.tokens = []
+
+        # Add the STREAM-START token.
+        self.fetch_stream_start()
+
+        # Number of tokens that were emitted through the `get_token` method.
+        self.tokens_taken = 0
+
+        # The current indentation level.
+        self.indent = -1
+
+        # Past indentation levels.
+        self.indents = []
+
+        # Variables related to simple keys treatment.
+
+        # A simple key is a key that is not denoted by the '?' indicator.
+        # Example of simple keys:
+        #   ---
+        #   block simple key: value
+        #   ? not a simple key:
+        #   : { flow simple key: value }
+        # We emit the KEY token before all keys, so when we find a potential
+        # simple key, we try to locate the corresponding ':' indicator.
+        # Simple keys should be limited to a single line and 1024 characters.
+
+        # Can a simple key start at the current position? A simple key may
+        # start:
+        # - at the beginning of the line, not counting indentation spaces
+        #       (in block context),
+        # - after '{', '[', ',' (in the flow context),
+        # - after '?', ':', '-' (in the block context).
+        # In the block context, this flag also signifies if a block collection
+        # may start at the current position.
+        self.allow_simple_key = True
+
+        # Keep track of possible simple keys. This is a dictionary. The key
+        # is `flow_level`; there can be no more that one possible simple key
+        # for each level. The value is a SimpleKey record:
+        #   (token_number, required, index, line, column, mark)
+        # A simple key may start with ALIAS, ANCHOR, TAG, SCALAR(flow),
+        # '[', or '{' tokens.
+        self.possible_simple_keys = {}
+
+    # Public methods.
+
+    def check_token(self, *choices):
+        # Check if the next token is one of the given types.
+        while self.need_more_tokens():
+            self.fetch_more_tokens()
+        if self.tokens:
+            if not choices:
+                return True
+            for choice in choices:
+                if isinstance(self.tokens[0], choice):
+                    return True
+        return False
+
+    def peek_token(self):
+        # Return the next token, but do not delete if from the queue.
+        # Return None if no more tokens.
+        while self.need_more_tokens():
+            self.fetch_more_tokens()
+        if self.tokens:
+            return self.tokens[0]
+        else:
+            return None
+
+    def get_token(self):
+        # Return the next token.
+        while self.need_more_tokens():
+            self.fetch_more_tokens()
+        if self.tokens:
+            self.tokens_taken += 1
+            return self.tokens.pop(0)
+
+    # Private methods.
+
+    def need_more_tokens(self):
+        if self.done:
+            return False
+        if not self.tokens:
+            return True
+        # The current token may be a potential simple key, so we
+        # need to look further.
+        self.stale_possible_simple_keys()
+        if self.next_possible_simple_key() == self.tokens_taken:
+            return True
+
+    def fetch_more_tokens(self):
+
+        # Eat whitespaces and comments until we reach the next token.
+        self.scan_to_next_token()
+
+        # Remove obsolete possible simple keys.
+        self.stale_possible_simple_keys()
+
+        # Compare the current indentation and column. It may add some tokens
+        # and decrease the current indentation level.
+        self.unwind_indent(self.column)
+
+        # Peek the next character.
+        ch = self.peek()
+
+        # Is it the end of stream?
+        if ch == '\0':
+            return self.fetch_stream_end()
+
+        # Is it a directive?
+        if ch == '%' and self.check_directive():
+            return self.fetch_directive()
+
+        # Is it the document start?
+        if ch == '-' and self.check_document_start():
+            return self.fetch_document_start()
+
+        # Is it the document end?
+        if ch == '.' and self.check_document_end():
+            return self.fetch_document_end()
+
+        # TODO: support for BOM within a stream.
+        #if ch == '\uFEFF':
+        #    return self.fetch_bom()    <-- issue BOMToken
+
+        # Note: the order of the following checks is NOT significant.
+
+        # Is it the flow sequence start indicator?
+        if ch == '[':
+            return self.fetch_flow_sequence_start()
+
+        # Is it the flow mapping start indicator?
+        if ch == '{':
+            return self.fetch_flow_mapping_start()
+
+        # Is it the flow sequence end indicator?
+        if ch == ']':
+            return self.fetch_flow_sequence_end()
+
+        # Is it the flow mapping end indicator?
+        if ch == '}':
+            return self.fetch_flow_mapping_end()
+
+        # Is it the flow entry indicator?
+        if ch == ',':
+            return self.fetch_flow_entry()
+
+        # Is it the block entry indicator?
+        if ch == '-' and self.check_block_entry():
+            return self.fetch_block_entry()
+
+        # Is it the key indicator?
+        if ch == '?' and self.check_key():
+            return self.fetch_key()
+
+        # Is it the value indicator?
+        if ch == ':' and self.check_value():
+            return self.fetch_value()
+
+        # Is it an alias?
+        if ch == '*':
+            return self.fetch_alias()
+
+        # Is it an anchor?
+        if ch == '&':
+            return self.fetch_anchor()
+
+        # Is it a tag?
+        if ch == '!':
+            return self.fetch_tag()
+
+        # Is it a literal scalar?
+        if ch == '|' and not self.flow_level:
+            return self.fetch_literal()
+
+        # Is it a folded scalar?
+        if ch == '>' and not self.flow_level:
+            return self.fetch_folded()
+
+        # Is it a single quoted scalar?
+        if ch == '\'':
+            return self.fetch_single()
+
+        # Is it a double quoted scalar?
+        if ch == '\"':
+            return self.fetch_double()
+
+        # It must be a plain scalar then.
+        if self.check_plain():
+            return self.fetch_plain()
+
+        # No? It's an error. Let's produce a nice error message.
+        raise ScannerError("while scanning for the next token", None,
+                "found character %r that cannot start any token" % ch,
+                self.get_mark())
+
+    # Simple keys treatment.
+
+    def next_possible_simple_key(self):
+        # Return the number of the nearest possible simple key. Actually we
+        # don't need to loop through the whole dictionary. We may replace it
+        # with the following code:
+        #   if not self.possible_simple_keys:
+        #       return None
+        #   return self.possible_simple_keys[
+        #           min(self.possible_simple_keys.keys())].token_number
+        min_token_number = None
+        for level in self.possible_simple_keys:
+            key = self.possible_simple_keys[level]
+            if min_token_number is None or key.token_number < min_token_number:
+                min_token_number = key.token_number
+        return min_token_number
+
+    def stale_possible_simple_keys(self):
+        # Remove entries that are no longer possible simple keys. According to
+        # the YAML specification, simple keys
+        # - should be limited to a single line,
+        # - should be no longer than 1024 characters.
+        # Disabling this procedure will allow simple keys of any length and
+        # height (may cause problems if indentation is broken though).
+        for level in list(self.possible_simple_keys):
+            key = self.possible_simple_keys[level]
+            if key.line != self.line  \
+                    or self.index-key.index > 1024:
+                if key.required:
+                    raise ScannerError("while scanning a simple key", key.mark,
+                            "could not find expected ':'", self.get_mark())
+                del self.possible_simple_keys[level]
+
+    def save_possible_simple_key(self):
+        # The next token may start a simple key. We check if it's possible
+        # and save its position. This function is called for
+        #   ALIAS, ANCHOR, TAG, SCALAR(flow), '[', and '{'.
+
+        # Check if a simple key is required at the current position.
+        required = not self.flow_level and self.indent == self.column
+
+        # The next token might be a simple key. Let's save it's number and
+        # position.
+        if self.allow_simple_key:
+            self.remove_possible_simple_key()
+            token_number = self.tokens_taken+len(self.tokens)
+            key = SimpleKey(token_number, required,
+                    self.index, self.line, self.column, self.get_mark())
+            self.possible_simple_keys[self.flow_level] = key
+
+    def remove_possible_simple_key(self):
+        # Remove the saved possible key position at the current flow level.
+        if self.flow_level in self.possible_simple_keys:
+            key = self.possible_simple_keys[self.flow_level]
+            
+            if key.required:
+                raise ScannerError("while scanning a simple key", key.mark,
+                        "could not find expected ':'", self.get_mark())
+
+            del self.possible_simple_keys[self.flow_level]
+
+    # Indentation functions.
+
+    def unwind_indent(self, column):
+
+        ## In flow context, tokens should respect indentation.
+        ## Actually the condition should be `self.indent >= column` according to
+        ## the spec. But this condition will prohibit intuitively correct
+        ## constructions such as
+        ## key : {
+        ## }
+        #if self.flow_level and self.indent > column:
+        #    raise ScannerError(None, None,
+        #            "invalid intendation or unclosed '[' or '{'",
+        #            self.get_mark())
+
+        # In the flow context, indentation is ignored. We make the scanner less
+        # restrictive then specification requires.
+        if self.flow_level:
+            return
+
+        # In block context, we may need to issue the BLOCK-END tokens.
+        while self.indent > column:
+            mark = self.get_mark()
+            self.indent = self.indents.pop()
+            self.tokens.append(BlockEndToken(mark, mark))
+
+    def add_indent(self, column):
+        # Check if we need to increase indentation.
+        if self.indent < column:
+            self.indents.append(self.indent)
+            self.indent = column
+            return True
+        return False
+
+    # Fetchers.
+
+    def fetch_stream_start(self):
+        # We always add STREAM-START as the first token and STREAM-END as the
+        # last token.
+
+        # Read the token.
+        mark = self.get_mark()
+        
+        # Add STREAM-START.
+        self.tokens.append(StreamStartToken(mark, mark,
+            encoding=self.encoding))
+        
+
+    def fetch_stream_end(self):
+
+        # Set the current intendation to -1.
+        self.unwind_indent(-1)
+
+        # Reset simple keys.
+        self.remove_possible_simple_key()
+        self.allow_simple_key = False
+        self.possible_simple_keys = {}
+
+        # Read the token.
+        mark = self.get_mark()
+        
+        # Add STREAM-END.
+        self.tokens.append(StreamEndToken(mark, mark))
+
+        # The steam is finished.
+        self.done = True
+
+    def fetch_directive(self):
+        
+        # Set the current intendation to -1.
+        self.unwind_indent(-1)
+
+        # Reset simple keys.
+        self.remove_possible_simple_key()
+        self.allow_simple_key = False
+
+        # Scan and add DIRECTIVE.
+        self.tokens.append(self.scan_directive())
+
+    def fetch_document_start(self):
+        self.fetch_document_indicator(DocumentStartToken)
+
+    def fetch_document_end(self):
+        self.fetch_document_indicator(DocumentEndToken)
+
+    def fetch_document_indicator(self, TokenClass):
+
+        # Set the current intendation to -1.
+        self.unwind_indent(-1)
+
+        # Reset simple keys. Note that there could not be a block collection
+        # after '---'.
+        self.remove_possible_simple_key()
+        self.allow_simple_key = False
+
+        # Add DOCUMENT-START or DOCUMENT-END.
+        start_mark = self.get_mark()
+        self.forward(3)
+        end_mark = self.get_mark()
+        self.tokens.append(TokenClass(start_mark, end_mark))
+
+    def fetch_flow_sequence_start(self):
+        self.fetch_flow_collection_start(FlowSequenceStartToken)
+
+    def fetch_flow_mapping_start(self):
+        self.fetch_flow_collection_start(FlowMappingStartToken)
+
+    def fetch_flow_collection_start(self, TokenClass):
+
+        # '[' and '{' may start a simple key.
+        self.save_possible_simple_key()
+
+        # Increase the flow level.
+        self.flow_level += 1
+
+        # Simple keys are allowed after '[' and '{'.
+        self.allow_simple_key = True
+
+        # Add FLOW-SEQUENCE-START or FLOW-MAPPING-START.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(TokenClass(start_mark, end_mark))
+
+    def fetch_flow_sequence_end(self):
+        self.fetch_flow_collection_end(FlowSequenceEndToken)
+
+    def fetch_flow_mapping_end(self):
+        self.fetch_flow_collection_end(FlowMappingEndToken)
+
+    def fetch_flow_collection_end(self, TokenClass):
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Decrease the flow level.
+        self.flow_level -= 1
+
+        # No simple keys after ']' or '}'.
+        self.allow_simple_key = False
+
+        # Add FLOW-SEQUENCE-END or FLOW-MAPPING-END.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(TokenClass(start_mark, end_mark))
+
+    def fetch_flow_entry(self):
+
+        # Simple keys are allowed after ','.
+        self.allow_simple_key = True
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Add FLOW-ENTRY.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(FlowEntryToken(start_mark, end_mark))
+
+    def fetch_block_entry(self):
+
+        # Block context needs additional checks.
+        if not self.flow_level:
+
+            # Are we allowed to start a new entry?
+            if not self.allow_simple_key:
+                raise ScannerError(None, None,
+                        "sequence entries are not allowed here",
+                        self.get_mark())
+
+            # We may need to add BLOCK-SEQUENCE-START.
+            if self.add_indent(self.column):
+                mark = self.get_mark()
+                self.tokens.append(BlockSequenceStartToken(mark, mark))
+
+        # It's an error for the block entry to occur in the flow context,
+        # but we let the parser detect this.
+        else:
+            pass
+
+        # Simple keys are allowed after '-'.
+        self.allow_simple_key = True
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Add BLOCK-ENTRY.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(BlockEntryToken(start_mark, end_mark))
+
+    def fetch_key(self):
+        
+        # Block context needs additional checks.
+        if not self.flow_level:
+
+            # Are we allowed to start a key (not necessary a simple)?
+            if not self.allow_simple_key:
+                raise ScannerError(None, None,
+                        "mapping keys are not allowed here",
+                        self.get_mark())
+
+            # We may need to add BLOCK-MAPPING-START.
+            if self.add_indent(self.column):
+                mark = self.get_mark()
+                self.tokens.append(BlockMappingStartToken(mark, mark))
+
+        # Simple keys are allowed after '?' in the block context.
+        self.allow_simple_key = not self.flow_level
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Add KEY.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(KeyToken(start_mark, end_mark))
+
+    def fetch_value(self):
+
+        # Do we determine a simple key?
+        if self.flow_level in self.possible_simple_keys:
+
+            # Add KEY.
+            key = self.possible_simple_keys[self.flow_level]
+            del self.possible_simple_keys[self.flow_level]
+            self.tokens.insert(key.token_number-self.tokens_taken,
+                    KeyToken(key.mark, key.mark))
+
+            # If this key starts a new block mapping, we need to add
+            # BLOCK-MAPPING-START.
+            if not self.flow_level:
+                if self.add_indent(key.column):
+                    self.tokens.insert(key.token_number-self.tokens_taken,
+                            BlockMappingStartToken(key.mark, key.mark))
+
+            # There cannot be two simple keys one after another.
+            self.allow_simple_key = False
+
+        # It must be a part of a complex key.
+        else:
+            
+            # Block context needs additional checks.
+            # (Do we really need them? They will be caught by the parser
+            # anyway.)
+            if not self.flow_level:
+
+                # We are allowed to start a complex value if and only if
+                # we can start a simple key.
+                if not self.allow_simple_key:
+                    raise ScannerError(None, None,
+                            "mapping values are not allowed here",
+                            self.get_mark())
+
+            # If this value starts a new block mapping, we need to add
+            # BLOCK-MAPPING-START.  It will be detected as an error later by
+            # the parser.
+            if not self.flow_level:
+                if self.add_indent(self.column):
+                    mark = self.get_mark()
+                    self.tokens.append(BlockMappingStartToken(mark, mark))
+
+            # Simple keys are allowed after ':' in the block context.
+            self.allow_simple_key = not self.flow_level
+
+            # Reset possible simple key on the current level.
+            self.remove_possible_simple_key()
+
+        # Add VALUE.
+        start_mark = self.get_mark()
+        self.forward()
+        end_mark = self.get_mark()
+        self.tokens.append(ValueToken(start_mark, end_mark))
+
+    def fetch_alias(self):
+
+        # ALIAS could be a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after ALIAS.
+        self.allow_simple_key = False
+
+        # Scan and add ALIAS.
+        self.tokens.append(self.scan_anchor(AliasToken))
+
+    def fetch_anchor(self):
+
+        # ANCHOR could start a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after ANCHOR.
+        self.allow_simple_key = False
+
+        # Scan and add ANCHOR.
+        self.tokens.append(self.scan_anchor(AnchorToken))
+
+    def fetch_tag(self):
+
+        # TAG could start a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after TAG.
+        self.allow_simple_key = False
+
+        # Scan and add TAG.
+        self.tokens.append(self.scan_tag())
+
+    def fetch_literal(self):
+        self.fetch_block_scalar(style='|')
+
+    def fetch_folded(self):
+        self.fetch_block_scalar(style='>')
+
+    def fetch_block_scalar(self, style):
+
+        # A simple key may follow a block scalar.
+        self.allow_simple_key = True
+
+        # Reset possible simple key on the current level.
+        self.remove_possible_simple_key()
+
+        # Scan and add SCALAR.
+        self.tokens.append(self.scan_block_scalar(style))
+
+    def fetch_single(self):
+        self.fetch_flow_scalar(style='\'')
+
+    def fetch_double(self):
+        self.fetch_flow_scalar(style='"')
+
+    def fetch_flow_scalar(self, style):
+
+        # A flow scalar could be a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after flow scalars.
+        self.allow_simple_key = False
+
+        # Scan and add SCALAR.
+        self.tokens.append(self.scan_flow_scalar(style))
+
+    def fetch_plain(self):
+
+        # A plain scalar could be a simple key.
+        self.save_possible_simple_key()
+
+        # No simple keys after plain scalars. But note that `scan_plain` will
+        # change this flag if the scan is finished at the beginning of the
+        # line.
+        self.allow_simple_key = False
+
+        # Scan and add SCALAR. May change `allow_simple_key`.
+        self.tokens.append(self.scan_plain())
+
+    # Checkers.
+
+    def check_directive(self):
+
+        # DIRECTIVE:        ^ '%' ...
+        # The '%' indicator is already checked.
+        if self.column == 0:
+            return True
+
+    def check_document_start(self):
+
+        # DOCUMENT-START:   ^ '---' (' '|'\n')
+        if self.column == 0:
+            if self.prefix(3) == '---'  \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                return True
+
+    def check_document_end(self):
+
+        # DOCUMENT-END:     ^ '...' (' '|'\n')
+        if self.column == 0:
+            if self.prefix(3) == '...'  \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                return True
+
+    def check_block_entry(self):
+
+        # BLOCK-ENTRY:      '-' (' '|'\n')
+        return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029'
+
+    def check_key(self):
+
+        # KEY(flow context):    '?'
+        if self.flow_level:
+            return True
+
+        # KEY(block context):   '?' (' '|'\n')
+        else:
+            return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029'
+
+    def check_value(self):
+
+        # VALUE(flow context):  ':'
+        if self.flow_level:
+            return True
+
+        # VALUE(block context): ':' (' '|'\n')
+        else:
+            return self.peek(1) in '\0 \t\r\n\x85\u2028\u2029'
+
+    def check_plain(self):
+
+        # A plain scalar may start with any non-space character except:
+        #   '-', '?', ':', ',', '[', ']', '{', '}',
+        #   '#', '&', '*', '!', '|', '>', '\'', '\"',
+        #   '%', '@', '`'.
+        #
+        # It may also start with
+        #   '-', '?', ':'
+        # if it is followed by a non-space character.
+        #
+        # Note that we limit the last rule to the block context (except the
+        # '-' character) because we want the flow context to be space
+        # independent.
+        ch = self.peek()
+        return ch not in '\0 \t\r\n\x85\u2028\u2029-?:,[]{}#&*!|>\'\"%@`'  \
+                or (self.peek(1) not in '\0 \t\r\n\x85\u2028\u2029'
+                        and (ch == '-' or (not self.flow_level and ch in '?:')))
+
+    # Scanners.
+
+    def scan_to_next_token(self):
+        # We ignore spaces, line breaks and comments.
+        # If we find a line break in the block context, we set the flag
+        # `allow_simple_key` on.
+        # The byte order mark is stripped if it's the first character in the
+        # stream. We do not yet support BOM inside the stream as the
+        # specification requires. Any such mark will be considered as a part
+        # of the document.
+        #
+        # TODO: We need to make tab handling rules more sane. A good rule is
+        #   Tabs cannot precede tokens
+        #   BLOCK-SEQUENCE-START, BLOCK-MAPPING-START, BLOCK-END,
+        #   KEY(block), VALUE(block), BLOCK-ENTRY
+        # So the checking code is
+        #   if <TAB>:
+        #       self.allow_simple_keys = False
+        # We also need to add the check for `allow_simple_keys == True` to
+        # `unwind_indent` before issuing BLOCK-END.
+        # Scanners for block, flow, and plain scalars need to be modified.
+
+        if self.index == 0 and self.peek() == '\uFEFF':
+            self.forward()
+        found = False
+        while not found:
+            while self.peek() == ' ':
+                self.forward()
+            if self.peek() == '#':
+                while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                    self.forward()
+            if self.scan_line_break():
+                if not self.flow_level:
+                    self.allow_simple_key = True
+            else:
+                found = True
+
+    def scan_directive(self):
+        # See the specification for details.
+        start_mark = self.get_mark()
+        self.forward()
+        name = self.scan_directive_name(start_mark)
+        value = None
+        if name == 'YAML':
+            value = self.scan_yaml_directive_value(start_mark)
+            end_mark = self.get_mark()
+        elif name == 'TAG':
+            value = self.scan_tag_directive_value(start_mark)
+            end_mark = self.get_mark()
+        else:
+            end_mark = self.get_mark()
+            while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                self.forward()
+        self.scan_directive_ignored_line(start_mark)
+        return DirectiveToken(name, value, start_mark, end_mark)
+
+    def scan_directive_name(self, start_mark):
+        # See the specification for details.
+        length = 0
+        ch = self.peek(length)
+        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                or ch in '-_':
+            length += 1
+            ch = self.peek(length)
+        if not length:
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        value = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        return value
+
+    def scan_yaml_directive_value(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        major = self.scan_yaml_directive_number(start_mark)
+        if self.peek() != '.':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a digit or '.', but found %r" % self.peek(),
+                    self.get_mark())
+        self.forward()
+        minor = self.scan_yaml_directive_number(start_mark)
+        if self.peek() not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a digit or ' ', but found %r" % self.peek(),
+                    self.get_mark())
+        return (major, minor)
+
+    def scan_yaml_directive_number(self, start_mark):
+        # See the specification for details.
+        ch = self.peek()
+        if not ('0' <= ch <= '9'):
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a digit, but found %r" % ch, self.get_mark())
+        length = 0
+        while '0' <= self.peek(length) <= '9':
+            length += 1
+        value = int(self.prefix(length))
+        self.forward(length)
+        return value
+
+    def scan_tag_directive_value(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        handle = self.scan_tag_directive_handle(start_mark)
+        while self.peek() == ' ':
+            self.forward()
+        prefix = self.scan_tag_directive_prefix(start_mark)
+        return (handle, prefix)
+
+    def scan_tag_directive_handle(self, start_mark):
+        # See the specification for details.
+        value = self.scan_tag_handle('directive', start_mark)
+        ch = self.peek()
+        if ch != ' ':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected ' ', but found %r" % ch, self.get_mark())
+        return value
+
+    def scan_tag_directive_prefix(self, start_mark):
+        # See the specification for details.
+        value = self.scan_tag_uri('directive', start_mark)
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected ' ', but found %r" % ch, self.get_mark())
+        return value
+
+    def scan_directive_ignored_line(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        if self.peek() == '#':
+            while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                self.forward()
+        ch = self.peek()
+        if ch not in '\0\r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a directive", start_mark,
+                    "expected a comment or a line break, but found %r"
+                        % ch, self.get_mark())
+        self.scan_line_break()
+
+    def scan_anchor(self, TokenClass):
+        # The specification does not restrict characters for anchors and
+        # aliases. This may lead to problems, for instance, the document:
+        #   [ *alias, value ]
+        # can be interpreted in two ways, as
+        #   [ "value" ]
+        # and
+        #   [ *alias , "value" ]
+        # Therefore we restrict aliases to numbers and ASCII letters.
+        start_mark = self.get_mark()
+        indicator = self.peek()
+        if indicator == '*':
+            name = 'alias'
+        else:
+            name = 'anchor'
+        self.forward()
+        length = 0
+        ch = self.peek(length)
+        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                or ch in '-_':
+            length += 1
+            ch = self.peek(length)
+        if not length:
+            raise ScannerError("while scanning an %s" % name, start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        value = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch not in '\0 \t\r\n\x85\u2028\u2029?:,]}%@`':
+            raise ScannerError("while scanning an %s" % name, start_mark,
+                    "expected alphabetic or numeric character, but found %r"
+                    % ch, self.get_mark())
+        end_mark = self.get_mark()
+        return TokenClass(value, start_mark, end_mark)
+
+    def scan_tag(self):
+        # See the specification for details.
+        start_mark = self.get_mark()
+        ch = self.peek(1)
+        if ch == '<':
+            handle = None
+            self.forward(2)
+            suffix = self.scan_tag_uri('tag', start_mark)
+            if self.peek() != '>':
+                raise ScannerError("while parsing a tag", start_mark,
+                        "expected '>', but found %r" % self.peek(),
+                        self.get_mark())
+            self.forward()
+        elif ch in '\0 \t\r\n\x85\u2028\u2029':
+            handle = None
+            suffix = '!'
+            self.forward()
+        else:
+            length = 1
+            use_handle = False
+            while ch not in '\0 \r\n\x85\u2028\u2029':
+                if ch == '!':
+                    use_handle = True
+                    break
+                length += 1
+                ch = self.peek(length)
+            handle = '!'
+            if use_handle:
+                handle = self.scan_tag_handle('tag', start_mark)
+            else:
+                handle = '!'
+                self.forward()
+            suffix = self.scan_tag_uri('tag', start_mark)
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a tag", start_mark,
+                    "expected ' ', but found %r" % ch, self.get_mark())
+        value = (handle, suffix)
+        end_mark = self.get_mark()
+        return TagToken(value, start_mark, end_mark)
+
+    def scan_block_scalar(self, style):
+        # See the specification for details.
+
+        if style == '>':
+            folded = True
+        else:
+            folded = False
+
+        chunks = []
+        start_mark = self.get_mark()
+
+        # Scan the header.
+        self.forward()
+        chomping, increment = self.scan_block_scalar_indicators(start_mark)
+        self.scan_block_scalar_ignored_line(start_mark)
+
+        # Determine the indentation level and go to the first non-empty line.
+        min_indent = self.indent+1
+        if min_indent < 1:
+            min_indent = 1
+        if increment is None:
+            breaks, max_indent, end_mark = self.scan_block_scalar_indentation()
+            indent = max(min_indent, max_indent)
+        else:
+            indent = min_indent+increment-1
+            breaks, end_mark = self.scan_block_scalar_breaks(indent)
+        line_break = ''
+
+        # Scan the inner part of the block scalar.
+        while self.column == indent and self.peek() != '\0':
+            chunks.extend(breaks)
+            leading_non_space = self.peek() not in ' \t'
+            length = 0
+            while self.peek(length) not in '\0\r\n\x85\u2028\u2029':
+                length += 1
+            chunks.append(self.prefix(length))
+            self.forward(length)
+            line_break = self.scan_line_break()
+            breaks, end_mark = self.scan_block_scalar_breaks(indent)
+            if self.column == indent and self.peek() != '\0':
+
+                # Unfortunately, folding rules are ambiguous.
+                #
+                # This is the folding according to the specification:
+                
+                if folded and line_break == '\n'    \
+                        and leading_non_space and self.peek() not in ' \t':
+                    if not breaks:
+                        chunks.append(' ')
+                else:
+                    chunks.append(line_break)
+                
+                # This is Clark Evans's interpretation (also in the spec
+                # examples):
+                #
+                #if folded and line_break == '\n':
+                #    if not breaks:
+                #        if self.peek() not in ' \t':
+                #            chunks.append(' ')
+                #        else:
+                #            chunks.append(line_break)
+                #else:
+                #    chunks.append(line_break)
+            else:
+                break
+
+        # Chomp the tail.
+        if chomping is not False:
+            chunks.append(line_break)
+        if chomping is True:
+            chunks.extend(breaks)
+
+        # We are done.
+        return ScalarToken(''.join(chunks), False, start_mark, end_mark,
+                style)
+
+    def scan_block_scalar_indicators(self, start_mark):
+        # See the specification for details.
+        chomping = None
+        increment = None
+        ch = self.peek()
+        if ch in '+-':
+            if ch == '+':
+                chomping = True
+            else:
+                chomping = False
+            self.forward()
+            ch = self.peek()
+            if ch in '0123456789':
+                increment = int(ch)
+                if increment == 0:
+                    raise ScannerError("while scanning a block scalar", start_mark,
+                            "expected indentation indicator in the range 1-9, but found 0",
+                            self.get_mark())
+                self.forward()
+        elif ch in '0123456789':
+            increment = int(ch)
+            if increment == 0:
+                raise ScannerError("while scanning a block scalar", start_mark,
+                        "expected indentation indicator in the range 1-9, but found 0",
+                        self.get_mark())
+            self.forward()
+            ch = self.peek()
+            if ch in '+-':
+                if ch == '+':
+                    chomping = True
+                else:
+                    chomping = False
+                self.forward()
+        ch = self.peek()
+        if ch not in '\0 \r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a block scalar", start_mark,
+                    "expected chomping or indentation indicators, but found %r"
+                    % ch, self.get_mark())
+        return chomping, increment
+
+    def scan_block_scalar_ignored_line(self, start_mark):
+        # See the specification for details.
+        while self.peek() == ' ':
+            self.forward()
+        if self.peek() == '#':
+            while self.peek() not in '\0\r\n\x85\u2028\u2029':
+                self.forward()
+        ch = self.peek()
+        if ch not in '\0\r\n\x85\u2028\u2029':
+            raise ScannerError("while scanning a block scalar", start_mark,
+                    "expected a comment or a line break, but found %r" % ch,
+                    self.get_mark())
+        self.scan_line_break()
+
+    def scan_block_scalar_indentation(self):
+        # See the specification for details.
+        chunks = []
+        max_indent = 0
+        end_mark = self.get_mark()
+        while self.peek() in ' \r\n\x85\u2028\u2029':
+            if self.peek() != ' ':
+                chunks.append(self.scan_line_break())
+                end_mark = self.get_mark()
+            else:
+                self.forward()
+                if self.column > max_indent:
+                    max_indent = self.column
+        return chunks, max_indent, end_mark
+
+    def scan_block_scalar_breaks(self, indent):
+        # See the specification for details.
+        chunks = []
+        end_mark = self.get_mark()
+        while self.column < indent and self.peek() == ' ':
+            self.forward()
+        while self.peek() in '\r\n\x85\u2028\u2029':
+            chunks.append(self.scan_line_break())
+            end_mark = self.get_mark()
+            while self.column < indent and self.peek() == ' ':
+                self.forward()
+        return chunks, end_mark
+
+    def scan_flow_scalar(self, style):
+        # See the specification for details.
+        # Note that we loose indentation rules for quoted scalars. Quoted
+        # scalars don't need to adhere indentation because " and ' clearly
+        # mark the beginning and the end of them. Therefore we are less
+        # restrictive then the specification requires. We only need to check
+        # that document separators are not included in scalars.
+        if style == '"':
+            double = True
+        else:
+            double = False
+        chunks = []
+        start_mark = self.get_mark()
+        quote = self.peek()
+        self.forward()
+        chunks.extend(self.scan_flow_scalar_non_spaces(double, start_mark))
+        while self.peek() != quote:
+            chunks.extend(self.scan_flow_scalar_spaces(double, start_mark))
+            chunks.extend(self.scan_flow_scalar_non_spaces(double, start_mark))
+        self.forward()
+        end_mark = self.get_mark()
+        return ScalarToken(''.join(chunks), False, start_mark, end_mark,
+                style)
+
+    ESCAPE_REPLACEMENTS = {
+        '0':    '\0',
+        'a':    '\x07',
+        'b':    '\x08',
+        't':    '\x09',
+        '\t':   '\x09',
+        'n':    '\x0A',
+        'v':    '\x0B',
+        'f':    '\x0C',
+        'r':    '\x0D',
+        'e':    '\x1B',
+        ' ':    '\x20',
+        '\"':   '\"',
+        '\\':   '\\',
+        '/':    '/',
+        'N':    '\x85',
+        '_':    '\xA0',
+        'L':    '\u2028',
+        'P':    '\u2029',
+    }
+
+    ESCAPE_CODES = {
+        'x':    2,
+        'u':    4,
+        'U':    8,
+    }
+
+    def scan_flow_scalar_non_spaces(self, double, start_mark):
+        # See the specification for details.
+        chunks = []
+        while True:
+            length = 0
+            while self.peek(length) not in '\'\"\\\0 \t\r\n\x85\u2028\u2029':
+                length += 1
+            if length:
+                chunks.append(self.prefix(length))
+                self.forward(length)
+            ch = self.peek()
+            if not double and ch == '\'' and self.peek(1) == '\'':
+                chunks.append('\'')
+                self.forward(2)
+            elif (double and ch == '\'') or (not double and ch in '\"\\'):
+                chunks.append(ch)
+                self.forward()
+            elif double and ch == '\\':
+                self.forward()
+                ch = self.peek()
+                if ch in self.ESCAPE_REPLACEMENTS:
+                    chunks.append(self.ESCAPE_REPLACEMENTS[ch])
+                    self.forward()
+                elif ch in self.ESCAPE_CODES:
+                    length = self.ESCAPE_CODES[ch]
+                    self.forward()
+                    for k in range(length):
+                        if self.peek(k) not in '0123456789ABCDEFabcdef':
+                            raise ScannerError("while scanning a double-quoted scalar", start_mark,
+                                    "expected escape sequence of %d hexdecimal numbers, but found %r" %
+                                        (length, self.peek(k)), self.get_mark())
+                    code = int(self.prefix(length), 16)
+                    chunks.append(chr(code))
+                    self.forward(length)
+                elif ch in '\r\n\x85\u2028\u2029':
+                    self.scan_line_break()
+                    chunks.extend(self.scan_flow_scalar_breaks(double, start_mark))
+                else:
+                    raise ScannerError("while scanning a double-quoted scalar", start_mark,
+                            "found unknown escape character %r" % ch, self.get_mark())
+            else:
+                return chunks
+
+    def scan_flow_scalar_spaces(self, double, start_mark):
+        # See the specification for details.
+        chunks = []
+        length = 0
+        while self.peek(length) in ' \t':
+            length += 1
+        whitespaces = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch == '\0':
+            raise ScannerError("while scanning a quoted scalar", start_mark,
+                    "found unexpected end of stream", self.get_mark())
+        elif ch in '\r\n\x85\u2028\u2029':
+            line_break = self.scan_line_break()
+            breaks = self.scan_flow_scalar_breaks(double, start_mark)
+            if line_break != '\n':
+                chunks.append(line_break)
+            elif not breaks:
+                chunks.append(' ')
+            chunks.extend(breaks)
+        else:
+            chunks.append(whitespaces)
+        return chunks
+
+    def scan_flow_scalar_breaks(self, double, start_mark):
+        # See the specification for details.
+        chunks = []
+        while True:
+            # Instead of checking indentation, we check for document
+            # separators.
+            prefix = self.prefix(3)
+            if (prefix == '---' or prefix == '...')   \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                raise ScannerError("while scanning a quoted scalar", start_mark,
+                        "found unexpected document separator", self.get_mark())
+            while self.peek() in ' \t':
+                self.forward()
+            if self.peek() in '\r\n\x85\u2028\u2029':
+                chunks.append(self.scan_line_break())
+            else:
+                return chunks
+
+    def scan_plain(self):
+        # See the specification for details.
+        # We add an additional restriction for the flow context:
+        #   plain scalars in the flow context cannot contain ',' or '?'.
+        # We also keep track of the `allow_simple_key` flag here.
+        # Indentation rules are loosed for the flow context.
+        chunks = []
+        start_mark = self.get_mark()
+        end_mark = start_mark
+        indent = self.indent+1
+        # We allow zero indentation for scalars, but then we need to check for
+        # document separators at the beginning of the line.
+        #if indent == 0:
+        #    indent = 1
+        spaces = []
+        while True:
+            length = 0
+            if self.peek() == '#':
+                break
+            while True:
+                ch = self.peek(length)
+                if ch in '\0 \t\r\n\x85\u2028\u2029'    \
+                        or (ch == ':' and
+                                self.peek(length+1) in '\0 \t\r\n\x85\u2028\u2029'
+                                      + (u',[]{}' if self.flow_level else u''))\
+                        or (self.flow_level and ch in ',?[]{}'):
+                    break
+                length += 1
+            if length == 0:
+                break
+            self.allow_simple_key = False
+            chunks.extend(spaces)
+            chunks.append(self.prefix(length))
+            self.forward(length)
+            end_mark = self.get_mark()
+            spaces = self.scan_plain_spaces(indent, start_mark)
+            if not spaces or self.peek() == '#' \
+                    or (not self.flow_level and self.column < indent):
+                break
+        return ScalarToken(''.join(chunks), True, start_mark, end_mark)
+
+    def scan_plain_spaces(self, indent, start_mark):
+        # See the specification for details.
+        # The specification is really confusing about tabs in plain scalars.
+        # We just forbid them completely. Do not use tabs in YAML!
+        chunks = []
+        length = 0
+        while self.peek(length) in ' ':
+            length += 1
+        whitespaces = self.prefix(length)
+        self.forward(length)
+        ch = self.peek()
+        if ch in '\r\n\x85\u2028\u2029':
+            line_break = self.scan_line_break()
+            self.allow_simple_key = True
+            prefix = self.prefix(3)
+            if (prefix == '---' or prefix == '...')   \
+                    and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                return
+            breaks = []
+            while self.peek() in ' \r\n\x85\u2028\u2029':
+                if self.peek() == ' ':
+                    self.forward()
+                else:
+                    breaks.append(self.scan_line_break())
+                    prefix = self.prefix(3)
+                    if (prefix == '---' or prefix == '...')   \
+                            and self.peek(3) in '\0 \t\r\n\x85\u2028\u2029':
+                        return
+            if line_break != '\n':
+                chunks.append(line_break)
+            elif not breaks:
+                chunks.append(' ')
+            chunks.extend(breaks)
+        elif whitespaces:
+            chunks.append(whitespaces)
+        return chunks
+
+    def scan_tag_handle(self, name, start_mark):
+        # See the specification for details.
+        # For some strange reasons, the specification does not allow '_' in
+        # tag handles. I have allowed it anyway.
+        ch = self.peek()
+        if ch != '!':
+            raise ScannerError("while scanning a %s" % name, start_mark,
+                    "expected '!', but found %r" % ch, self.get_mark())
+        length = 1
+        ch = self.peek(length)
+        if ch != ' ':
+            while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                    or ch in '-_':
+                length += 1
+                ch = self.peek(length)
+            if ch != '!':
+                self.forward(length)
+                raise ScannerError("while scanning a %s" % name, start_mark,
+                        "expected '!', but found %r" % ch, self.get_mark())
+            length += 1
+        value = self.prefix(length)
+        self.forward(length)
+        return value
+
+    def scan_tag_uri(self, name, start_mark):
+        # See the specification for details.
+        # Note: we do not check if URI is well-formed.
+        chunks = []
+        length = 0
+        ch = self.peek(length)
+        while '0' <= ch <= '9' or 'A' <= ch <= 'Z' or 'a' <= ch <= 'z'  \
+                or ch in '-;/?:@&=+$,_.!~*\'()[]%':
+            if ch == '%':
+                chunks.append(self.prefix(length))
+                self.forward(length)
+                length = 0
+                chunks.append(self.scan_uri_escapes(name, start_mark))
+            else:
+                length += 1
+            ch = self.peek(length)
+        if length:
+            chunks.append(self.prefix(length))
+            self.forward(length)
+            length = 0
+        if not chunks:
+            raise ScannerError("while parsing a %s" % name, start_mark,
+                    "expected URI, but found %r" % ch, self.get_mark())
+        return ''.join(chunks)
+
+    def scan_uri_escapes(self, name, start_mark):
+        # See the specification for details.
+        codes = []
+        mark = self.get_mark()
+        while self.peek() == '%':
+            self.forward()
+            for k in range(2):
+                if self.peek(k) not in '0123456789ABCDEFabcdef':
+                    raise ScannerError("while scanning a %s" % name, start_mark,
+                            "expected URI escape sequence of 2 hexdecimal numbers, but found %r"
+                            % self.peek(k), self.get_mark())
+            codes.append(int(self.prefix(2), 16))
+            self.forward(2)
+        try:
+            value = bytes(codes).decode('utf-8')
+        except UnicodeDecodeError as exc:
+            raise ScannerError("while scanning a %s" % name, start_mark, str(exc), mark)
+        return value
+
+    def scan_line_break(self):
+        # Transforms:
+        #   '\r\n'      :   '\n'
+        #   '\r'        :   '\n'
+        #   '\n'        :   '\n'
+        #   '\x85'      :   '\n'
+        #   '\u2028'    :   '\u2028'
+        #   '\u2029     :   '\u2029'
+        #   default     :   ''
+        ch = self.peek()
+        if ch in '\r\n\x85':
+            if self.prefix(2) == '\r\n':
+                self.forward(2)
+            else:
+                self.forward()
+            return '\n'
+        elif ch in '\u2028\u2029':
+            self.forward()
+            return ch
+        return ''
diff --git a/libs/yaml/serializer.py b/libs/yaml/serializer.py
new file mode 100644
index 000000000..fe911e67a
--- /dev/null
+++ b/libs/yaml/serializer.py
@@ -0,0 +1,111 @@
+
+__all__ = ['Serializer', 'SerializerError']
+
+from .error import YAMLError
+from .events import *
+from .nodes import *
+
+class SerializerError(YAMLError):
+    pass
+
+class Serializer:
+
+    ANCHOR_TEMPLATE = 'id%03d'
+
+    def __init__(self, encoding=None,
+            explicit_start=None, explicit_end=None, version=None, tags=None):
+        self.use_encoding = encoding
+        self.use_explicit_start = explicit_start
+        self.use_explicit_end = explicit_end
+        self.use_version = version
+        self.use_tags = tags
+        self.serialized_nodes = {}
+        self.anchors = {}
+        self.last_anchor_id = 0
+        self.closed = None
+
+    def open(self):
+        if self.closed is None:
+            self.emit(StreamStartEvent(encoding=self.use_encoding))
+            self.closed = False
+        elif self.closed:
+            raise SerializerError("serializer is closed")
+        else:
+            raise SerializerError("serializer is already opened")
+
+    def close(self):
+        if self.closed is None:
+            raise SerializerError("serializer is not opened")
+        elif not self.closed:
+            self.emit(StreamEndEvent())
+            self.closed = True
+
+    #def __del__(self):
+    #    self.close()
+
+    def serialize(self, node):
+        if self.closed is None:
+            raise SerializerError("serializer is not opened")
+        elif self.closed:
+            raise SerializerError("serializer is closed")
+        self.emit(DocumentStartEvent(explicit=self.use_explicit_start,
+            version=self.use_version, tags=self.use_tags))
+        self.anchor_node(node)
+        self.serialize_node(node, None, None)
+        self.emit(DocumentEndEvent(explicit=self.use_explicit_end))
+        self.serialized_nodes = {}
+        self.anchors = {}
+        self.last_anchor_id = 0
+
+    def anchor_node(self, node):
+        if node in self.anchors:
+            if self.anchors[node] is None:
+                self.anchors[node] = self.generate_anchor(node)
+        else:
+            self.anchors[node] = None
+            if isinstance(node, SequenceNode):
+                for item in node.value:
+                    self.anchor_node(item)
+            elif isinstance(node, MappingNode):
+                for key, value in node.value:
+                    self.anchor_node(key)
+                    self.anchor_node(value)
+
+    def generate_anchor(self, node):
+        self.last_anchor_id += 1
+        return self.ANCHOR_TEMPLATE % self.last_anchor_id
+
+    def serialize_node(self, node, parent, index):
+        alias = self.anchors[node]
+        if node in self.serialized_nodes:
+            self.emit(AliasEvent(alias))
+        else:
+            self.serialized_nodes[node] = True
+            self.descend_resolver(parent, index)
+            if isinstance(node, ScalarNode):
+                detected_tag = self.resolve(ScalarNode, node.value, (True, False))
+                default_tag = self.resolve(ScalarNode, node.value, (False, True))
+                implicit = (node.tag == detected_tag), (node.tag == default_tag)
+                self.emit(ScalarEvent(alias, node.tag, implicit, node.value,
+                    style=node.style))
+            elif isinstance(node, SequenceNode):
+                implicit = (node.tag
+                            == self.resolve(SequenceNode, node.value, True))
+                self.emit(SequenceStartEvent(alias, node.tag, implicit,
+                    flow_style=node.flow_style))
+                index = 0
+                for item in node.value:
+                    self.serialize_node(item, node, index)
+                    index += 1
+                self.emit(SequenceEndEvent())
+            elif isinstance(node, MappingNode):
+                implicit = (node.tag
+                            == self.resolve(MappingNode, node.value, True))
+                self.emit(MappingStartEvent(alias, node.tag, implicit,
+                    flow_style=node.flow_style))
+                for key, value in node.value:
+                    self.serialize_node(key, node, None)
+                    self.serialize_node(value, node, key)
+                self.emit(MappingEndEvent())
+            self.ascend_resolver()
+
diff --git a/libs/yaml/tokens.py b/libs/yaml/tokens.py
new file mode 100644
index 000000000..4d0b48a39
--- /dev/null
+++ b/libs/yaml/tokens.py
@@ -0,0 +1,104 @@
+
+class Token(object):
+    def __init__(self, start_mark, end_mark):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+    def __repr__(self):
+        attributes = [key for key in self.__dict__
+                if not key.endswith('_mark')]
+        attributes.sort()
+        arguments = ', '.join(['%s=%r' % (key, getattr(self, key))
+                for key in attributes])
+        return '%s(%s)' % (self.__class__.__name__, arguments)
+
+#class BOMToken(Token):
+#    id = '<byte order mark>'
+
+class DirectiveToken(Token):
+    id = '<directive>'
+    def __init__(self, name, value, start_mark, end_mark):
+        self.name = name
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class DocumentStartToken(Token):
+    id = '<document start>'
+
+class DocumentEndToken(Token):
+    id = '<document end>'
+
+class StreamStartToken(Token):
+    id = '<stream start>'
+    def __init__(self, start_mark=None, end_mark=None,
+            encoding=None):
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.encoding = encoding
+
+class StreamEndToken(Token):
+    id = '<stream end>'
+
+class BlockSequenceStartToken(Token):
+    id = '<block sequence start>'
+
+class BlockMappingStartToken(Token):
+    id = '<block mapping start>'
+
+class BlockEndToken(Token):
+    id = '<block end>'
+
+class FlowSequenceStartToken(Token):
+    id = '['
+
+class FlowMappingStartToken(Token):
+    id = '{'
+
+class FlowSequenceEndToken(Token):
+    id = ']'
+
+class FlowMappingEndToken(Token):
+    id = '}'
+
+class KeyToken(Token):
+    id = '?'
+
+class ValueToken(Token):
+    id = ':'
+
+class BlockEntryToken(Token):
+    id = '-'
+
+class FlowEntryToken(Token):
+    id = ','
+
+class AliasToken(Token):
+    id = '<alias>'
+    def __init__(self, value, start_mark, end_mark):
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class AnchorToken(Token):
+    id = '<anchor>'
+    def __init__(self, value, start_mark, end_mark):
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class TagToken(Token):
+    id = '<tag>'
+    def __init__(self, value, start_mark, end_mark):
+        self.value = value
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+
+class ScalarToken(Token):
+    id = '<scalar>'
+    def __init__(self, value, plain, start_mark, end_mark, style=None):
+        self.value = value
+        self.plain = plain
+        self.start_mark = start_mark
+        self.end_mark = end_mark
+        self.style = style
+