'If we have no real user, we should send back failure response.'

def test_real_user_is_none(self):

    self.xmodule.verify_oauth_body_sign = Mock()
    self.xmodule.has_score = True
    self.system.get_real_user = Mock(return_value=None)
    request = Request(self.environ)
    request.body = self.get_request_body()
    response = self.xmodule.grade_handler(request, '')
    real_response = self.get_response_values(response)
    expected_response = {'action': None, 'code_major': 'failure', 'description': 'User    not    found.', 'messageIdentifier': self.defaults['messageIdentifier']}
    self.assertEqual(response.status_code, 200)
    self.assertDictEqual(expected_response, real_response)
