Bug Fixes

- Fixed MongoDB driver so that it passes unchanged
- Fixed Cassandra Mocking so that it passes unchanged
Bug Fix

- Cassandra needs to initialize the reftime by inserting it without changing the refcounts
Enhancement - Test Cleanup

- Update sqlite driver tests to use self.assert*
Pep8 Compliance
Bug Fixes

- Forgot the NotImplementedError for the abstract version
- Added test when the block doesn't exist to exercise the exception handling