Unit tests fail with new model class.

[rjekker]

Adding a model class in the unit tests, users seem to get permissions they should not have.

See the following commit on my forked project: https://github.com/rjekker/django-rules/commit/27179a1303074fce675e2bc2558c0cdd0b70d6f7

I create a new Model class with permissions in tests/testapp/models.py:

    @rules.predicate
    def is_car_owner(user, car):
        return car.owner == user

    class Car(RulesModel):
        owner = models.ForeignKey(get_user_model(), on_delete=models.CASCADE)

        class Meta:
            rules_permissions = {"wash": rules.always_allow,
                                 "drive": is_car_owner,
                                 "crash": rules.always_deny

I create two car instances with different owners:

        if sys.version_info.major >= 3:
            from testapp.models import Car
            Car.objects.create(
                owner=adrian
            )
            Car.objects.create(
                owner=martin
            )

Then the following test fails:

    def test_cars_owner(self):
        # adrian can *not* drive martins car
        car1 = Car.objects.get(pk=1)
        assert car1.owner.username == "adrian"
        car2 = Car.objects.get(pk=2)
        assert car2.owner.username == "martin"
        adrian = get_user_model().objects.get(pk=1)
        martin = get_user_model().objects.get(pk=2)
        assert adrian == car1.owner
        assert martin == car2.owner

        assert not adrian.has_perm(Car.get_perm("drive"), car2) # <---- Fails here
        assert not martin.has_perm(Car.get_perm("drive"), car1)

The unit test seems to decide that adrian can drive martins car, even though he should not.