catch possible exception.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@36554 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/DivergenceMessage.py

@@ -93,9 +93,12 @@ class DivergenceMessage(ObjectMessage):
     return None
 
   def __eq__(self, other):
-    return self.__dict__ == other.__dict__
+    try:
+      return self.__dict__ == other.__dict__
+    except AttributeError:
+      return False
 
   def __ne__(self, other):
-    return self.__dict__ != other.__dict__
+    return not self.__eq__(other)
 
 allow_class(DivergenceMessage)