Fix DictMix missing in py3

CorePost/corepost/convert.py

@@ -9,7 +9,6 @@ for JSON/XML/YAML output
 import collections
 import logging
 import json
-from UserDict import DictMixin
 from twisted.python import log
 
 primitives = (int, long, float, bool, str,unicode)
@@ -20,7 +19,7 @@ def convertForSerialization(obj):
         if type(obj) in primitives:
         # no conversion
             return obj 
-        elif isinstance(obj, dict) or isinstance(obj,DictMixin):
+        elif isinstance(obj, dict):
             return traverseDict(obj)
         elif isClassInstance(obj):
             return convertClassToDict(obj)
@@ -66,7 +65,7 @@ def convertToJson(obj):
     
 def generateXml(obj):
     """Generates basic XML from an object that has already been converted for serialization"""
-    if isinstance(obj, dict) or isinstance(obj,DictMixin):
+    if isinstance(obj, dict):
         return getXML_dict(obj, "item")
     elif isinstance(obj,collections.Iterable):
         return "<list>%s</list>" % getXML(obj, "item")