private function unlockOrLockUsers(Dropzone $dropzone, $unlock = true)
    {
        $this->get('icap.manager.dropzone_voter')->isAllowToOpen($dropzone);
        $this->get('icap.manager.dropzone_voter')->isAllowToEdit($dropzone);

        $dropRepo = $this->getDoctrine()->getManager()->getRepository('IcapDropzoneBundle:Drop');
        $drops = $dropRepo->findBy(['dropzone' => $dropzone->getId(), 'unlockedUser' => !$unlock]);

        foreach ($drops as $drop) {
            $drop->setUnlockedUser($unlock);
        }
        $em = $this->getDoctrine()->getManager();
        $em->flush();

        return $this->redirect(
            $this->generateUrl(
                'icap_dropzone_examiners',
                [
                    'resourceId' => $dropzone->getId(),
                ]
            )
        );
    }