Transaction patching gets stomped on by django's TestCase

[dgouldin]

When using johnny cache with django's TestCase, johnny cache's transaction patching gets overridden by TestCase's patching. This results in johnny cache's local cache not being cleared between tests, creating all kinds of problems.

[acjay]

I think I may have encountered this issue too. I ended up having to invalidate the table manually multiple times before every request, because the change to the cache only "sticks" the first request after invalidation.