protected function githubToken($userToken)
    {
        $token = $userToken ?: getenv(self::TOKEN_ENV);

        if (!$token) {
            throw new \RuntimeException(sprintf(
                'Could not find GitHub auth token. Please set the environment ' .
                'variable `%s` or pass token as console argument.',
                self::TOKEN_ENV
            ));
        }

        return $token;
    }