Webpack: SASS + ExtractTextPligin error on Linux?

Question

webpack

Good evening gentlemen. I have 2 OS - Windows 10 and Ubuntu 16.04.3. I'm slowly pissing with Webpack, the builds are not difficult, but today I launched the build on Ubuntu, which I used on Windows and got errors, but the build builds fine.
As I understand it, the error appears due to the 'extract-text-webpack-plugin' plugin, since without it, styles without errors are put inline.
Screenshot of the error in the terminal:

webpack.config.js:

const path = require('path');
const ExtractTextPlugin = require("extract-text-webpack-plugin");
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {

  entry: {
    'app': path.join(__dirname, 'src', 'app')
  },

  output: {
    path: path.join(__dirname, 'dist'),
    filename: '[name].js'
  },

  module: {
    rules: [
      {
        test: /\.scss$/,
        use: [{
          loader: "style-loader" // creates style nodes from JS strings
        }, {
          loader: "css-loader" // translates CSS into CommonJS
        }, {
          loader: "sass-loader",
          options: {
            includePaths: [path.join(__dirname, 'src', 'app.scss')]
          }
        }]
      },

      {
        test: /\.scss$/,
        use: ExtractTextPlugin.extract({
          fallback: 'style-loader',
          use: ['css-loader', 'sass-loader']
        })
      }
    ]
  },

  plugins: [
    new HtmlWebpackPlugin({
      filename: 'index.html',
      template: path.join(__dirname, 'src', 'index.html')
    }),

    new ExtractTextPlugin('css/app.css')
  ]

};

What could be the problem? I would like to fully understand this.

Answer 1

It's simple, you have a rule twice that tells webpack to process scss. Remove excess.
Those. in your case, leave it with Extract...
Just in case, here's your own piece (webpack 2+):

{
        test: /\.scss$/,
        loader: ExtractTextPlugin.extract({
          fallbackLoader: 'style-loader',
          loader: ['css-loader', 'postcss-loader', 'sass-loader'],
          publicPath: '/public',
        }),
      },