Django AssertTemplateUsed test fails since Upgrade to Django 1.8

Since updating from Django 1.7.x to Django 1.8.x, my tests fail when checking for the right template. I'm using a ResearchFactory:

class AdminUnitTest(TestCase):
    """Sets up the testing environment for an admin"""

    def setUp(self):
        self.factory = RequestFactory()
        user = User.objects.create_user(
            username="cj123",
            email="chuck.jones@acme.edu",
            password="xxx",
            first_name="Chuck",
            last_name="Jones"
        )
        admin = Staff.objects.create(user=user, role='admin')
        self.user = user

The actual test then looks like this:

class YearViewTest(AdminUnitTest):
    def test_year_view_uses_right_template(self):
        request = self.factory.get('/year_view/all')
        request.user = self.user
        response = year_view(request, 'all')
        self.assertTemplateUsed(response, 'year_view.html')

This approach worked perfectly fine, until the update to 1.8. Since then I get the following error:

ValueError: assertTemplateUsed() and assertTemplateNotUsed() are only usable on responses fetched using the Django test Client.

In Django's source code (http://ift.tt/1M9dfas) I can only find this condition raising the error I get:

if template_name is not None and response is not None and not hasattr(response, 'templates'):
    raise ValueError(
            "assertTemplateUsed() and assertTemplateNotUsed() are only "
            "usable on responses fetched using the Django test Client."
        )

I struggle to see where my error there is. Can anyone help me?