webpackConfig.module.loaders.push({
  test: /\.module\.sass$/,
  loader: path.join(path.dirname(require.resolve('extract-text-webpack-plugin')), 'loader.js') + '?{"remove":true}!css?sourceMap&modules&localIdentName=[local]___[hash:base64:5]&-autoprefixer!' + 'postcss-loader!'+ 'sass-loader?sourceMap'
});
webpackConfig.module.loaders.forEach(function(loader, index) {
  if (typeof loader.test === 'function' && loader.test.toString().indexOf('\\.sass$') > -1) {
    loader.include = /node_modules/;
    loader.test = /\.sass$/;
  }
  if (loader.test.toString() === '/\\.module\\.sass$/') {
    loader.exclude = /node_modules/;
    loader.test = /\.sass$/;
  }
})

 webpackConfig.module.loaders.push({

                               ^

TypeError: Cannot read property 'push' of undefined