webpack 打包失败

报错：
The CLI moved into a separate package：webpack-cli
Would you like to install webpack-cli ( That will run npm install -D webpack-cli )
( yes/No )
解决方案：

• webpack 已经更新，webpack 4.0 之后 命令行单独分出一个包，webpack-cli，安装webpack-cli 包。

npm install webpack-cli -g

• 安装指定版本，如安装 2.4.1 版
  

npm install [email protected] -g