ExceptionLoggingSubscriber::onException

public ExceptionLoggingSubscriber::onException(GetResponseForExceptionEvent $event)

public function onException(GetResponseForExceptionEvent $event) {
  $exception = $event->getException();

  $method = 'onError';

  // Treat any non-HTTP exception as if it were one, so we log it the same.
  if ($exception instanceof HttpExceptionInterface) {
    $possible_method = 'on' . $exception->getStatusCode();
    if (method_exists($this, $possible_method)) {
      $method = $possible_method;
    }
  }

  $this->$method($event);
}