private function runCommandOnServers(array $remote_servers, Git_Driver_Gerrit_MembershipCommand $command)
 {
     foreach ($remote_servers as $remote_server) {
         try {
             $command->execute($remote_server);
         } catch (Git_Driver_Gerrit_Exception $e) {
             $this->logger->error($e->getMessage());
         }
     }
 }