【业务涉及思路】基本的错误拦截处理

case 400: err.message = '请求错误(400)'; break;
case 401: err.message = '未授权，请重新登录(401)'; break;
case 403: err.message = '拒绝访问(403)'; break;
case 404: err.message = '请求出错(404)'; break;
case 408: err.message = '请求超时(408)'; break;
case 500: err.message = '服务器错误(500)'; break;
case 501: err.message = '服务未实现(501)'; break;
case 502: err.message = '网络错误(502)'; break;
case 503: err.message = '服务不可用(503)'; break;
case 504: err.message = '网络超时(504)'; break;
case 505: err.message = 'HTTP版本不受支持(505)'; break;