public function error($exception)
    {
        $response = new Response();

        // Set the default error response
        $response->setContent('There has been a problem serving this request.');
        $response->headers->set('content-type', 'text/html');
        $response->setStatusCode(Response::HTTP_INTERNAL_SERVER_ERROR);

        // Execute the user defined error callback
        if (is_callable($this->error)) {
            $response = call_user_func($this->error, $response, $exception);
        }

        // Send the response
        $response->send();
    }