public function findPlatformRoles(User $user)
    {
        $dql = "
            SELECT r FROM Claroline\CoreBundle\Entity\Role r
            JOIN r.users u
            WHERE u.id = {$user->getId()} AND r.type = ".Role::PLATFORM_ROLE;
        $query = $this->_em->createQuery($dql);

        return $query->getResult();
    }