fix[cssnano]:use official demo of webpack config to avoid temporary bug of build:prod. ps:I have a computer which build:prod well but another computer throw cssnano error. The most amazing thing is that my two computers are same type and project is the same branch. Finally, I add the official config to branch for solving this problem and it works well.

build/webpack.prod.conf.js

@@ -9,7 +9,7 @@ const CopyWebpackPlugin = require('copy-webpack-plugin')
 const HtmlWebpackPlugin = require('html-webpack-plugin')
 const ScriptExtHtmlWebpackPlugin = require('script-ext-html-webpack-plugin')
 const MiniCssExtractPlugin = require('mini-css-extract-plugin')
-// const OptimizeCSSAssetsPlugin = require('optimize-css-assets-webpack-plugin')
+const OptimizeCSSAssetsPlugin = require('optimize-css-assets-webpack-plugin')
 const UglifyJsPlugin = require('uglifyjs-webpack-plugin')
 
 function resolve(dir) {
@@ -140,7 +140,15 @@ const webpackConfig = merge(baseWebpackConfig, {
       }),
       // Compress extracted CSS. We are using this plugin so that possible
       // duplicated CSS from different components can be deduped.
-      // new OptimizeCSSAssetsPlugin()
+      new OptimizeCSSAssetsPlugin({
+        assetNameRegExp: /\.optimize\.css$/g,
+        cssProcessor: require('cssnano'),
+        cssProcessorOptions: {
+          safe: true,
+          discardComments: { removeAll: true }
+        },
+        canPrint: true
+      })
     ]
   }
 })