title: How to suppress warnings using webpack and post css
body: <p>How do I suppress warnings generated by webpack loading post css files?</p>
  
  <p>Warning example:</p>
  
  <pre><code>WARNING in ./~/css-loader!./~/postcss-loader!./src/components/Navigator/Navigator.css
  postcss-custom-properties: C:\StackData\bd\src\components\Navigator\Navigator.css:33:9: variable '--active' is undefined and
   used without a fallback
  </code></pre>
  
  <p>My webpack config:</p>
  
  <pre><code> module: {
      loaders: [
     ...
        {test: /\.css/, loader: 'style-loader!css-loader!postcss-loader'},
     ...
      ]
    },
    postcss: function () {
      return [precss, autoprefixer];
    }
  </code></pre>