title: FatalErrorException: Error: Class 'Symfony\Component\Debug\Exception\FlattenException' not found
body: <p>I use sonata admin/userBundle and FosUserBundle but when I check the profile page "/profile",I get this strange error :</p>
  
  <pre><code>FatalErrorException: Error: Class 'Symfony\Component\Debug\Exception\FlattenException' not found in /var/www/project/vendor/sonata-project/user-bundle/Sonata/UserBundle/Block/ProfileMenuBlockService.php line 97
  </code></pre>