module object has not attribute JSONEncoder

[ghjim]

My root WSGI page is now throwing the error:

"AttributeError at /  module object has no attribute JSONEncoder"

I have seen several posts about this with implications that it might be a Python bug.  It started occurring  to me after I
did a number of system updates.  I have been unable to back out and get my web page working again
(this will teach me to do better regression testing when I update my systems).

The error is thrown by /opt/django/Django-1.4.3/django/contrib/messages/storage/cookie.py.  There is a reference to
class MessageEncoder(json.JSONEncoder).

If I do a directory of json I see an attribute with this name:

python
>>>import json
>>>names=dir(json)
>>>print names

I am using Python2.7.3 which installs both json and simplejson.

If anybody has seen this I would appreciate some help.