The unit tests for the gravatar template tags were living in

djblets.gravatars.templatetags.tests, which was getting loaded when

Django loaded the list of available template tags.
This in turn caused all test-related code to load, including kgb. This

resulted in failures in production.
These tests have now been moved into djblets.gravatars.tests.

Unit tests pass.
Deployed to production and didn't hit the import issues.