Add support for generating sqlite files during repo metadata generation
1099771 - Add a unit test to assert correct behavior for reporting invalid checksums.

We had a bug reported against 2.3[0] wherein a module was not being used correctly. It turns out that this was already fixed in 2.4, but there was
still no unit test coverage on the code that caused the exception. This commit adds coverage to that code.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1099771
Merge branch 'pulp-2.4' into barnabycourt-sqlite
Update for PR comments
Make sure that generate_sqlite is supported for exported repositories as well
Update to prevent test break on rhel6
Update for python 2.6 compatibility
Merge branch 'rbarlow-1099771' into pulp-2.4
Merge branch 'barnabycourt-sqlite' into pulp-2.4
Merge branch 'pulp-2.4' into master