Backported from the trunk, on Raymond's request:

SF bug #849662.  Dramatically, improve comparison speed for "if shl == None".

Lib/UserDict.py

@@ -155,6 +155,8 @@ class DictMixin:
     def __repr__(self):
         return repr(dict(self.iteritems()))
     def __cmp__(self, other):
+        if other is None:
+            return 1
         if isinstance(other, DictMixin):
             other = dict(other.iteritems())
         return cmp(dict(self.iteritems()), other)