Get rid of mutable default arguments

Author: gsnedders

html5lib/html5parser.py

@@ -253,8 +253,10 @@ def parseFragment(self, stream, container="div", encoding=None,
         self._parse(stream, True, container=container, encoding=encoding)
         return self.tree.getFragment()
 
-    def parseError(self, errorcode="XXX-undefined-error", datavars={}):
+    def parseError(self, errorcode="XXX-undefined-error", datavars=None):
         # XXX The idea is to make errorcode mandatory.
+        if datavars is None:
+            datavars = {}
         self.errors.append((self.tokenizer.stream.position(), errorcode, datavars))
         if self.strict:
             raise ParseError(E[errorcode] % datavars)

html5lib/treebuilders/etree_lxml.py

@@ -193,7 +193,9 @@ def __init__(self, namespaceHTMLElements, fullTree=False):
         self.namespaceHTMLElements = namespaceHTMLElements
 
         class Attributes(dict):
-            def __init__(self, element, value={}):
+            def __init__(self, element, value=None):
+                if value is None:
+                    value = {}
                 self._element = element
                 dict.__init__(self, value)
                 for key, value in self.items():