protected function executeExistingCommand(
        $command_name,
        InputInterface $input = null,
        OutputInterface $output = null
    ) {
        if (!isset($command_name)) {
            return 1;
        }
        $input = isset($input) ? $input : $this->input();
        $output = isset($output) ? $output : $this->output();

        return $this->getApplication()
            ->find($command_name)
            ->run($input, $output);
    }