/**
  * @param $statusCode
  * @param $url
  * @param RequestInterface $request
  * @param Response $response
  */
 public function validate($statusCode, $url, RequestInterface $request, Response $response)
 {
     if ($response->getStatusCode() === $statusCode) {
         return;
     }
     $message = $url . ' gives a non-200 status code response.';
     $this->logger->warning($message, array('request' => (string) $request, 'response' => (string) $response));
     throw new RuntimeException($message . ' See logs.' . $response->serialize());
 }