webpack 用 webpack-parallel-uglify-plugin 加速打包报错

用 UglifyJsPlugin 可以正常打包，就是很慢

new webpack.optimize.UglifyJsPlugin({
   compress: {
     warnings: false
   },
   sourceMap: true
}),

用 ParallelUglifyPlugin 加速打包之后

new ParallelUglifyPlugin({
      cacheDir: '.cache/',
      uglifyJS: {
        output: {
          comments: false
        },
        compress: {
          warnings: false
        }
      },
      sourceMap: config.build.productionSourceMap
    }),

打包失败，报错

ERROR in Encountered an error while minifying static/js/0.feb0ac937597219abdc1.js:
`warnings` is not a supported option

将：
compress: {
warnings: false
}
改为：
warnings: false

new ParallelUglifyPlugin({
      cacheDir: '.cache/',
      uglifyJS:{
        output: {
          comments: false
        },
        warnings: false,
        compress: {
          drop_debugger: true,
          drop_console: true
        }
      }
    }),