老师，为什么出现了这个错误Failed at the es6-webpack@1.0.0 start script.

npm start

> es6-webpack@1.0.0 start C:\Users\admin\es6-webpack
> webpack-dev-server --open

'webpack-dev-server' ▒▒▒▒▒ڲ▒▒▒▒ⲿ▒▒▒Ҳ▒▒▒ǿ▒▒▒▒еij▒▒▒
▒▒▒▒▒▒▒▒▒ļ▒▒▒
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! es6-webpack@1.0.0 start: `webpack-dev-server --open`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the es6-webpack@1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above