title: File permission on composer update
body: <p>The <strong>app/cache</strong> and <strong>app/logs</strong> folder mode has been set to 0777. And apache run user and group same with cli user. Running</p>
  
  <pre><code>php app/console cache-clear
  </code></pre>
  
  <p>works fine as well. But the problem is when composer update, I always get:</p>
  
  <blockquote>
    <p>[InvalidArgumentException]<br>
    The directory
    "/home/userx/symfony/app/cache/dev/annotations" is not
    writable. Both, the webserver and the console user need access. You
    can manage access rights for multiple users with "chmod +a". If your
    system does not support this, check out the acl package.              </p>
    
    <p>cache:clear [--no-warmup] [--no-optional-warmers]</p>
    
    <p>Script
    Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache
    handling the post-update-cmd event terminated with an exception</p>
    
    <p>[RuntimeException]<br>
    An error occurred when executing the "'cache:clear --no-warmup'"
    command.</p>
  </blockquote>
  
  <p>What could be the issue ?
  Thanks.</p>