'Get the UsageKey from the response payload and verify that the status_code was 200.
:param response:'

def response_usage_key(self, response):

    parsed = json.loads(response.content)
    self.assertEqual(response.status_code, 200)
    key = UsageKey.from_string(parsed['locator'])
    if (key.course_key.run is None):
        key = key.map_into_course(CourseKey.from_string(parsed['courseKey']))
    return key
