如何更改laravel 5 json错误消息格式？

<?php

namespace App\Exceptions;

use Exception;
use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;
use Illuminate\Http\JsonResponse;

class JsonExceptionHandler extends ExceptionHandler
{
    /**
     * Render an exception into an HTTP response.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Exception  $exception
     * @return \Illuminate\Http\JsonResponse
     */
    public function render($request, Exception $exception)
    {
        if ($request->expectsJson()) {
            return new JsonResponse([
                'error' => [
                    'code' => $exception->getCode(),
                    'message' => $exception->getMessage(),
                ],
            ], 400);
        }

        return parent::render($request, $exception);
    }
}

use App\Exceptions\JsonExceptionHandler;

class Handler extends ExceptionHandler
{
    // ...

    /**
     * Render an exception into an HTTP response.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Exception  $exception
     * @return \Illuminate\Http\Response|\Illuminate\Http\JsonResponse
     */
    public function render($request, Exception $exception)
    {
        if ($this->isHttpException($exception)) {
            return $this->toIlluminateResponse($this->renderHttpException($exception), $exception);
        } else {
            return (new JsonExceptionHandler($this->container))->render($request, $exception);
        }
    }

    // ...
}