Don't rely on the ElementTree Comment factory being the tag attribute on Comments.

This is needed for xml.etree.cElementTree under 2.6 (and likely hence custom
installs of cElementTree 1.2), where the tag property is equal to
xml.etree.ElementTree.Comment (i.e., the pure Python version).

Similarly, don't rely on type(comment.tag), as this is just function!

Author: gsnedders

html5lib/treebuilders/etree.py

@@ -13,6 +13,7 @@
 
 def getETreeBuilder(ElementTreeImplementation, fullTree=False):
     ElementTree = ElementTreeImplementation
+    ElementTreeCommentType = ElementTree.Comment("asd").tag
     class Element(_base.Node):
         def __init__(self, name, namespace=None):
             self._name = name
@@ -207,7 +208,7 @@ def serializeElement(element, indent=0):
                     rv.append("|%s\"%s\""%(' '*(indent+2), element.text))
                 if element.tail:
                     finalText = element.tail
-            elif element.tag == ElementTree.Comment:
+            elif element.tag == ElementTreeCommentType:
                 rv.append("|%s<!-- %s -->"%(' '*indent, element.text))
             else:
                 assert isinstance(element.tag, text_type), "Expected unicode, got %s, %s"%(type(element.tag), element.tag)
@@ -275,7 +276,7 @@ def serializeElement(element):
                 for child in element:
                     serializeElement(child)
 
-            elif type(element.tag) == type(ElementTree.Comment):
+            elif element.tag == ElementTreeCommentType:
                 rv.append("<!--%s-->"%(element.text,))
             else:
                 #This is assumed to be an ordinary element