Conforming to Django 1.6+ special timeout values

Django 1.6+: Explicitly passing in timeout=None will set a non-expiring timeout. Passing in timeout=0 will set-and-expire-immediately the value.

I didn’t know tox. The tox output was so verbose that I can’t tell if my commit passed the tests or not…
Oh off course, you’re right. "Bien vu !" I realized what you mean when starting to write add() tests. Tests are useful ;)