title: Symfony2 Assetic CSS rewriting breaks on url(data:image...)
body: <p>I faced a problem with Assetic's CSS rewrite. It works fine in the sense it makes the URLs correct, however, it also ruins <code>data:image</code> URLs like this:</p>
  
  <pre><code>background: url('data:image/svg+xml;base64,PD94bWw...');
  </code></pre>
  
  <p>into:</p>
  
  <pre><code>background: url('../../bundles/proj/css/data:image/svg+xml;base64,PD94bWw...');
  </code></pre>
  
  <p>Is there a workaround or a fix to this?</p>