'Assert that the given response was an error for the access_token field with the given error message.'

def _assert_access_token_error(self, response, expected_error_message):

    self.assertEqual(response.status_code, 400)
    response_json = json.loads(response.content)
    self.assertEqual(response_json, {'access_token': [{'user_message': expected_error_message}]})
