/**
  * Gets the list of test takers assigned to a delivery
  *
  * @throws \common_Exception
  * @throws \oat\oatbox\service\ServiceNotFoundException
  */
 public function deliveryTestTakers()
 {
     try {
         $delivery = $this->getCurrentDelivery();
         $testCenter = $this->getCurrentTestCenter();
         $requestOptions = $this->getRequestOptions();
         $this->returnJson(DeliveryHelper::getDeliveryTestTakers($delivery, $testCenter->getUri(), $requestOptions));
     } catch (ServiceNotFoundException $e) {
         \common_Logger::w('No delivery service defined for proctoring');
         $this->returnError('Proctoring interface not available');
     }
 }