Remove direct dependency on User model in Unit Tests

[CorwinTanner]

This seems like a great library. Unfortunately, I can't use it yet as it will not pass our automated unit testing since we are using a custom user model. Please replace direct references to Django's User model with django.contrib.auth.get_user_model().

Thank you.

[synasius]

Hi

[masci]

@CorwinTanner thanks for the report. The fix will be shipped with the next release, in the meantime you can check out the master branch and see if it works for you.

[CorwinTanner]

Thank you for the quick turnaround!