/**
  * @param $username
  * @return User|null
  */
 public function getUserByUsername($username)
 {
     try {
         $query = new \CultureFeed_SearchUsersQuery();
         $query->nick = $username;
         $results = $this->cultureFeed->searchUsers($query);
         $users = $results->objects;
         if (empty($users)) {
             return null;
         }
         $user = reset($users);
         return $this->getUser($user->id);
     } catch (\CultureFeed_ParseException $e) {
         return null;
     }
 }