错误如下：
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! travel@1.0.0 dev: `webpack-dev-server --inline --progress --config build/webpack.dev.conf.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the travel@1.0.0 dev script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?
npm ERR! A complete log of this run can be found in:
npm ERR! D:\Program Files\nodejs\node_cache\_logs\2018-08-01T09_05_17_312Z-debug.log
原因：这是新版webpack存在的BUG，卸载现有的新版本webpack，装老版本就好。
（1）、npm uninstall webpack-dev-server
（2）、npm install webpack-dev-server@2.9.1
（3）、npm run dev
