public function run()
    {
        // NOTE: To be removed in v1.0.0. Use "ErrorHandlerIntegration" instead.
        if (static::$container->has(self::ERROR_HANDLER)) {
            $debugger = static::$container->get(self::ERROR_HANDLER);

            $debugger->display();
        }

        $request = static::$container->get(self::SERVER_REQUEST);

        echo (string) $this->emit($request)->getBody();
    }