Fixed unit tests for Django queries that use exact/aggregate expressions that aren't associated with a speicific Field.
Fixed unit tests for Django queries that use exact/aggregate expressions that aren't associated with a speicific Field.

Stranger6667/django-hstore,djangonauts/django-hstore,Stranger6667/django-hstore,pombredanne/django-hstore,djangonauts/django-hstore,Stranger6667/django-hstore,Stranger6667/django-hstore,pombredanne/django-hstore,pombredanne/django-hstore,djangonauts/django-hstore,pombredanne/django-hstore,djangonauts/django-hstore