message: add safe option to css minifier
diff: @@ -291,7 +291,10 @@ module.exports = function makeWebpackConfig() {
  new OptimizeCssAssetsPlugin({
  assetNameRegExp: /\.css$/g,
  cssProcessor: require('cssnano'),
  - cssProcessorOptions: { discardComments: {removeAll: true } },
  + cssProcessorOptions: {
  + discardComments: {removeAll: true },
  + safe: true
  + },
  canPrint: true
  })
  );
  