title: webpack-dev-server exits with status code 1
body: <p>I have three files webpack.config.base, webpack.config.dev, webpack.config.prod with respective code:</p>
  
  <p>** webpack.config.base**</p>
  
  <pre><code>const webpack = require('webpack');
  const path = require('path');
  const ExtractTextPlugin = require('extract-text-webpack-plugin');
  
  const parentDir = path.join(__dirname, '../');
  
  module.exports = {
    entry: [
      path.join(parentDir, 'index.js'),
    ],
    resolve: {
      extensions: ['.js', '.jsx', '.json'],
    },
    module: {
      rules: [
        {
          test: /\.(js|jsx)$/,
          exclude: /node_modules/,
          loader: 'babel-loader',
        },
        {
          test: /\.(png|jpg|jpeg|gif|svg|woff|woff2)$/,
          use: [
            {
              loader: 'image-webpack-loader',
              options: {
                bypassOnDebug: true,
              },
            },
            'url-loader?limit=10000',
          ],
        },
        {
          test: /\.scss$/,
          loader: ExtractTextPlugin.extract({
            fallback: 'style-loader',
            use: ['css-loader', 'sass-loader'],
          }),
        },
      ],
    },
    output: {
      path: `${parentDir}/dist`,
      filename: 'bundle.js',
    },
    plugins: [
      new ExtractTextPlugin({
        filename: 'main.css',
      }),
      new webpack.DefinePlugin({
        'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV || 'development'),
      }),
      new webpack.optimize.OccurrenceOrderPlugin(),
      new webpack.NoEmitOnErrorsPlugin(),
    ],
  };
  </code></pre>
  
  <p>** webpack.config.dev**</p>
  
  <pre><code>    const webpack = require('webpack');
  const merge = require('webpack-merge');
  const path = require('path');
  
  const parentDir = path.join(__dirname, '../');
  const config = require('./webpack.config.base.js');
  
  module.exports = merge(config, {
  
    devServer: {
      inline: true,
      colors: true,
      progress: true,
      hot: true,
      open: true,
      bail: true,
      quiet: true,
      contentBase: parentDir,
      port: 7070,
      historyApiFallback: true,
    },
  
    plugins: [
      new webpack.HotModuleReplacementPlugin(),
    ],
  });
  </code></pre>
  
  <p>Production:</p>
  
  <pre><code>const webpack = require('webpack');
  
  const config = require('./webpack.config.base.js');
  
  config.plugins = config.plugins.concat([
    new webpack.optimize.DedupePlugin(),
    new webpack.optimize.UglifyJsPlugin({ mangle: false, sourcemap: false }),
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify('production'),
    }),
  ]);
  
  module.exports = config;
  </code></pre>
  
  <p>Script in package.json is</p>
  
  <pre><code> "dev": "./node_modules/.bin/webpack-dev-server --mode development --config ./webpack/webpack.config.dev.js",
  </code></pre>
  
  <p>On using npm run dev webpack dev server exits with status code-1. can anybody please tell where I'm getting wrong? Versions I am using is:</p>
  
  <pre><code>"webpack": "^4.6.0",
  "webpack-cli": "^2.1.2",
  "webpack-dev-server": "^3.1.4"
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/4VQqA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4VQqA.png" alt="Error:"></a></p>
  
  <p>Thanks in advance. I have tried using this same in single file and it runs well, but when divided like this in three different files that time it creates this error. All these files are in webpack folder at root directory.</p>