title: Facing error while building app with "Webpack": 4, LoadConfigError: Cannot find module 'sigmund'
body: <p>I'm using Webpack 4 and getting error when I'm building my app.
  I have also attached both snapshot of the error that I'm facing and Webpack configuration code.</p>
  
  <p>Please help me to resolve this issue.
  I'm using:
  OS: Ubuntu 18.04,
  Webpack: 4
  NodeJs: NodeJS LTS 10,
  NPM: 5.6.0</p>
  
  <p><a href="https://i.stack.imgur.com/mVAm1.png" rel="nofollow noreferrer">Snapshot of error here</a></p>
  
  <p>My Webpack.config.prod.js Config:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var webpack = require('webpack');
  var path = require('path');
  var BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;
  // var OfflinePlugin = require('offline-plugin')
  // const CompressionPlugin = require("compression-webpack-plugin")
  const UglifyJsPlugin = require('uglifyjs-webpack-plugin')
  const MiniCssExtractPlugin = require("mini-css-extract-plugin");
  const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
  
  module.exports = {
    entry: {
      '/js/app': './frontend/app.js'
    },
    output: {
      filename: 'app.js',
      chunkFilename: '[name].js',
      publicPath: "/public/js/",
      path: path.resolve(__dirname, 'public', 'js')
    },
    module: {
      rules: [
        {
          test: /jquery.+\.js$/,
          use: [{
              loader: 'expose-loader',
              options: 'jQuery'
          },{
              loader: 'expose-loader',
              options: '$'
          }]
        },
        {
          test: /\.(scss|css|sass)$/i,
  
          use: [
            // {
            //   loader: MiniCssExtractPlugin.loader,
            //   options: {
            //     // you can specify a publicPath here
            //     // by default it use publicPath in webpackOptions.output
            //     publicPath: '../'
            //   }
            // },
            {
              loader: "style-loader"
            },
            {
              loader: "css-loader"
            },
            {
              loader: "sass-loader",
              options: {
                includePaths: [
                  path.resolve("./node_modules/")
              ]
            }
          }
        ]
      },
      {
        test: /\.js$/,
        loader: "babel-loader",
        include: [
          path.resolve(__dirname, "frontend"),
        ],
        exclude: [
          path.resolve(__dirname, "node_modules")
        ],
      },
      {
        test: /\.(eot|woff|woff2|ttf|svg|png|jpg|gif)$/,
        loader: 'url-loader?limit=4096&amp;name=[name]-[hash].[ext]'
      },
      {
        test: /\.json$/,
        loader: 'json-loader',
        type: "javascript/auto"
      }
    ]},
    node: {
      fs: "empty",
      net: "empty"
    },
    optimization: {
      minimizer: [new UglifyJsPlugin()]
    },
    performance: {
      maxEntrypointSize: 512000,
      maxAssetSize: 512000
    },
    plugins: [
      new BundleAnalyzerPlugin({
        analyzerHost: "0.0.0.0"
      }),
      new UglifyJsPlugin({
        test: /\.js(\?.*)?$/i,
        parallel: true,
        extractComments: 'all'
      }),
      new MiniCssExtractPlugin({
        filename: "[name].css",
        chunkFilename: "[id].css"
      }),
      new webpack.ProvidePlugin({
        jQuery: 'jquery',
        $: 'jquery',
        jquery: 'jquery',
        'window.jQuery': 'jquery',
        Popper: ['popper.js', 'default'],
      }),
      new webpack.DefinePlugin({
        'process.env.NODE_ENV': JSON.stringify('production')
      }),
      new OptimizeCSSAssetsPlugin({
        assetNameRegExp: /\.optimize\.css$/g,
        cssProcessor: require('cssnano'),
        cssProcessorPluginOptions: {
          preset: ['default', { discardComments: { removeAll: true } }],
        },
        canPrint: true
      })
      ]
      }</code></pre>
  </div>
  </div>
  </p>