nnect which will result in a new response.</li>
 <li>503 - with invalid or missing <code><a href="../core/HttpHeaders.html#RETRY_AFTER">"Retry-After"</a></code> header: This is an error
 condition. <code>onError</code> is invoked.</li>
 <li>Any other status code: This is an error condition. <code>onError</code> is invoked.</li>
 </ul>
 <p>
 In the case of an error condition response, the <code>Throwable</code> passed to the <code>onError</code> consumer
 <i>should</i> be a WebApplicationException containing