code: public function exception(Request $request)
      {
          $ex = $request->getException();
          
          $this->response->setCode(500);
          printf("<h2>%s</h2>", HttpStatus::getStatus(500));
          while ($ex != null) {
              printf("<h3>%s</h3><pre>%s</pre>", $ex->getMessage(), $ex->getTraceAsString());
              $ex = $ex->getPrevious();
          }
      }
docs: Error processing for exceptions
  
  @param Request $request
  The request which contains an exception