protected function loadPrivateKey($key)
    {
        if (app()->runningUnitTests()) {
            return '===FAKE-KEY===';
        }

        // If it's a relative path, start searching in the
        // project root
        if ($key[0] !== '/') {
            $key = base_path().'/'.$key;
        }

        return file_get_contents($key);
    }