public static function makeFromSerial()
    {
        $contents = file_get_contents(HTMLPURIFIER_PREFIX . '/HTMLPurifier/ConfigSchema/schema.ser');
        $r = unserialize($contents);
        if (!$r) {
            $hash = sha1($contents);
            trigger_error("Unserialization of configuration schema failed, sha1 of file was $hash", E_USER_ERROR);
        }
        return $r;
    }