private function getBrowser($browserOption = null)
    {
        if (!empty($browserOption)) {
            list($command, ) = explode(' ', $browserOption, 2);
            if (!$this->shell->commandExists($command)) {
                $this->stdErr->writeln(sprintf('Command not found: <error>%s</error>', $command));
                return false;
            }

            return $browserOption;
        }

        return $this->getDefaultBrowser();
    }