'Tests "redirect_url" is None if change_enrollment returns a HttpResponse
with no content'

def test_change_enrollment_200_no_redirect(self):

    extra_post_params = {'enrollment_action': 'enroll'}
    with patch('student.views.change_enrollment') as mock_change_enrollment:
        mock_change_enrollment.return_value = HttpResponse()
        (response, _) = self._login_response('test@edx.org', 'test_password', extra_post_params=extra_post_params)
    response_content = json.loads(response.content)
    self.assertIsNone(response_content['redirect_url'])
    self._assert_response(response, success=True)
