title: compass/sass issues using Symfony2
body: <p>I am new in using compass and I'd like to use it with sass in my symfony2 project.</p>
  
  <p>I googled how to set the project:
  - Installed ruby
  - then install Compass/sass.</p>
  
  <p>Assetic bundle is installed, and then I added in the conf.yml:</p>
  
  <pre><code>parameters:
    assetic.filter.compass.images_dir: %kernel.root_dir%/../web/img
    assetic.filter.compass.http_path:  /img
  assetic:
    debug:          "%kernel.debug%"
    use_controller: false
    bundles:        [ ]
    filters:
      cssrewrite: ~
      #sass and compass assetic conf
      sass:
          bin: /usr/local/bin/sass
      compass:
          bin: /usr/local/bin/compass
  </code></pre>
  
  <p>And finally I add in my html.twig</p>
  
  <pre><code>{% stylesheets filter="compass" output="assets/css/styles.css"  "@lbTestBundle/Resources/assets/sass/*.scss" %}
          &lt;link rel="stylesheet" href="{{ asset_url }}" /&gt;
      {% endstylesheets %}
  </code></pre>
  
  <p>when i use the command "assetic:dump" the css file is create but I got the following error :</p>
  
  <pre><code>Error Output:
  /usr/bin/ruby: No such file or directory -- /usr/local/bin/compass (LoadError)
  </code></pre>
  
  <p>And my css is empty.</p>
  
  <p>Did I missed something? If someone can help me thanks.</p>