code: public void responseSendError(int statusCode, String message) throws IOException {
  
          if (defaultExternalContext != null) {
              defaultExternalContext.responseSendError(statusCode, message);
          } else {
              throw new UnsupportedOperationException();
          }
          
      }
docs: <p class="changed_added_2_0">Sends an HTTP status code with message.</p>
  
  <p><em>Servlet:</em> This must be performed by calling the
  <code>javax.servlet.http.HttpServletResponse</code> <code>sendError</code>
  method.</p>
  
  <p>The default implementation throws
  <code>UnsupportedOperationException</code> and is provided for
  the sole purpose of not breaking existing applications that
  extend this class.</p>
  
  @param statusCode an HTTP status code
  @param message an option message to detail the cause of the code
  
  @since 2.0