public function getDigitalOcean($file = self::DEFAULT_CREDENTIALS_FILE)
    {
        if (!file_exists($file)) {
            throw new \RuntimeException(sprintf('Impossible to get credentials informations in %s', $file));
        }

        $credentials = Yaml::parse($file);

        return new DigitalOcean(new Credentials($credentials['CLIENT_ID'], $credentials['API_KEY']));
    }