code: protected function exceptionPage(\Exception $e) : string
      {
          $exStr = ExceptionUtil::toString($e);
  
          $content = <<<HTML
  
      <h2>Mayday!</h2>
      <div>
      <b>{$e->getMessage()}</b> @ {$e->getFile()}:{$e->getLine()}
      </div>
      <pre>{$exStr}</pre>
  HTML;
  
          return self::page($content);
      }
docs: @param \Exception $e
  
  @return string