title: "Unknown word" error showing after adding postcss-loader
body: <p>I am trying to add <code>postcss loader</code> in my <em>webpack</em> but after adding <code>postcss loader</code> showing <strong><code>Unknown word error</code></strong>.
  I also attached error screenshot. please find attachment. 
  Not sure what error is.... <a href="https://i.stack.imgur.com/Nd1Bg.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/Nd1Bg.jpg" alt="enter image description here"></a></p>
  
  <p>I also added <code>postcss-loader</code>, <code>sass-loader</code> ,<code>css-loader</code> ,<code>style-loader</code>. If i am doing anything wrong please tell me guys.</p>
  
  <p>Below is my loaders in config file and package.json file.</p>
  
  <pre><code>  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: ["babel-loader", "ts-loader", "tslint-loader"]
  
      },
      {
        test: /\.css$/,
        include: __dirname + "./src/css",
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: {
              modules: true,
              importLoaders: 1
            }
          },
          'postcss-loader',
  
        ]
      },
      {
        test: /\.scss$/,
        use: [
          "style-loader",
          {
            loader: "css-loader",
            options: {
              sourceMap: isDevMode
            }
          },
          {
            loader: "sass-loader",
            options: {
              sourceMap: isDevMode
            }
          }
        ]
      },
  
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          isDevMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          'css-loader',
          'sass-loader',
        ],
      },
  
      {
        loader: 'postcss-loader',
        options: {
          plugins: () =&gt; [require('autoprefixer')],
          loader: "postcss-loader",
        }
      },
  
      {
        test: /\.(ttf|eot|woff|woff2)$/,
        use: {
          loader: "file-loader",
          options: {
            name: "fonts/[name].[ext]",
          },
        },
      },
      {
        test: /\.(jpe?g|png|gif|svg|ico)$/i,
        use: [
          {
            loader: "file-loader",
            options: {
              outputPath: "assets/"
            }
          }
        ]
      },
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: [
          'babel-loader'
        ]
      }
  
    ]
  },
  </code></pre>
  
  <p>package.json</p>
  
  <pre><code>"dependencies": {
  
      "cssnano": "4.0.5",
      "postcss-cssnext": "3.1.0",
      "postcss-import": "12.0.0",
      "prop-types": "15.6.0",
      "react": "15.6.2",
      "react-dom": "15.4.2",
      "react-redux": "4.4.9",
      "react-router": "3.0.2",
      "react-router-dom": "4.2.2",
      "redux": "^3.5.2",
      "redux-logger": "^2.6.1",
      "redux-promise": "^0.5.3",
      "redux-react-session": "2.2.0",
      "redux-thunk": "2.3.0",
      "sugarss": "2.0.0",
      "superagent": "3.8.1"
    },
    "devDependencies": {
  
      "autoprefixer": "^9.0.2",
      "babel-loader": "^7.1.4",
      "clean-webpack-plugin": "^0.1.19",
      "css-loader": "^0.28.11",
      "eslint": "3.15.0",
      "extract-text-webpack-plugin": "1.0.1",
      "file-loader": "^1.1.11",
      "html-webpack-plugin": "^3.1.0",
      "mini-css-extract-plugin": "0.4.2",
      "open": "0.0.5",
      "postcss-loader": "^3.0.0",
      "sass-loader": "^7.0.3",
      "style-loader": "^0.20.3",
      "webpack": "4.17.1",
      "webpack-dev-middleware": "1.6.1",
      "webpack-dev-server": "3.1.5",
      "webpack-hot-middleware": "2.12.2",
      "webpack-md5-hash": "0.0.5"
    },
  </code></pre>