code: protected function callHandler($handler, Exception $exception)
  	{
  		if ($handler instanceof ErrorHandlerInterface) {
  			return $handler->handle($exception);
  		}
  
  		return call_user_func($handler, $exception);
  	}
docs: Call an exception handler.
  
  @param  mixed     $handler
  @param  Exception $exception
  
  @return mixed