Update Beautiful Soup

lib/bs4/builder/_html5lib.py

@@ -8,6 +8,7 @@ __all__ = [
 import warnings
 import re
 from bs4.builder import (
+    DetectsXMLParsedAsHTML,
     PERMISSIVE,
     HTML,
     HTML_5,
@@ -69,13 +70,26 @@ class HTML5TreeBuilder(HTMLTreeBuilder):
         # 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.")
+            warnings.warn(
+                "You provided a value for exclude_encoding, but the html5lib tree builder doesn't support exclude_encoding.",
+                stacklevel=3
+            )
+
+        # html5lib only parses HTML, so if it's given XML that's worth
+        # noting.
+        DetectsXMLParsedAsHTML.warn_if_markup_looks_like_xml(
+            markup, stacklevel=3
+        )
+
         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.")
+            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.",
+                stacklevel=4
+            )
         parser = html5lib.HTMLParser(tree=self.create_treebuilder)
         self.underlying_builder.parser = parser
         extra_kwargs = dict()
@@ -242,10 +256,10 @@ class AttrList(object):
     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['*']
+        list_attr = self.element.cdata_list_attributes or {}
+        if (name in list_attr.get('*', [])
             or (self.element.name in list_attr
-                and name in list_attr[self.element.name])):
+                and name in list_attr.get(self.element.name, []))):
             # A node that is being cloned may have already undergone
             # this procedure.
             if not isinstance(value, list):