我已经下载了webpack-cli了，但是依然报错。蒙蔽了

D:\web\products\webpackTest2>webpack-cli -v
2.0.10

D:\web\products\webpackTest2>webpack-dev-server -v
The CLI moved into a separate package: webpack-cli.
Please install 'webpack-cli' in addition to webpack itself to use the CLI.
-> When using npm: npm install webpack-cli -D
-> When using yarn: yarn add webpack-cli -D
module.js:540
    throw err;
    ^

Error: Cannot find module 'webpack-cli/bin/config-yargs'
    at Function.Module._resolveFilename (module.js:538:15)
    at Function.Module._load (module.js:468:25)
    at Module.require (module.js:587:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (D:\web\products\webpackTest2\node_modules\_webpack-dev-server@3.1.0@webpack-dev-server\bin\webpack-dev-server.js:65:1)
    at Module._compile (module.js:643:30)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)
    at tryModuleLoad (module.js:499:12)
    at Function.Module._load (module.js:491:3)