code: public function kernelException(GetResponseForExceptionEvent $event)
      {
          $exception = $event->getException();
  
          if ($exception instanceof ValidationException) {
              return;
          }
  
          $data = [
              'type' => 'https://tools.ietf.org/html/rfc2616#section-10',
              'title' =>'An error occurred'
          ];
  
          if (in_array($this->environment, ['dev', 'test'], true)) {
              $data['detail'] = $exception->getMessage();
              $data['trace'] = $exception->getTrace();
          }
  
          $request = $event->getRequest();
          $contentTypes = $request->getAcceptableContentTypes();
          $accept = array_shift($contentTypes);
  
          switch ($accept) {
              case 'application/json':
              case 'application/ld+json':
                  $code = Response::HTTP_INTERNAL_SERVER_ERROR;
  
                  if ($exception instanceof HttpException) {
                      $code = $exception->getStatusCode();
                  }
  
                  $response = new JsonResponse($data, $code);
                  $event->setResponse($response);
                  break;
          }
      }
docs: Format uncaught exceptions into the proper format based on request
  
  @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event