title: How to define nested static directories in app.yaml?
body: <p>I have static directory "/static", with js and css files, and inside it another directory "images". How can I define this in app.yaml so that images are accessible from js and css files using relative directories? For example, in "/static/main.css":</p>
  
  <pre><code>.bck {background-image: url(images/img.png); }
  </code></pre>
  
  <p>Should refer to "/static/images/img.png".</p>
  
  <p>The following doesn't work:</p>
  
  <pre><code>handlers:
  
  - url: /static
    static_dir: static
  
  - url: /static/images
    static_dir: static/images
  </code></pre>