Return a "hashed" form of the hostname, as used by OpenSSH when storing
        hashed hostnames in the known_hosts file.

        :param str hostname: the hostname to hash
        :param str salt: optional salt to use when hashing (must be 20 bytes long)
        :return: the hashed hostname as a `str`

def hash_host(hostname, salt=None):
        """
        Return a "hashed" form of the hostname, as used by OpenSSH when storing
        hashed hostnames in the known_hosts file.

        :param str hostname: the hostname to hash
        :param str salt: optional salt to use when hashing (must be 20 bytes long)
        :return: the hashed hostname as a `str`
        """
        if salt is None:
            salt = os.urandom(sha1().digest_size)
        else:
            if salt.startswith('|1|'):
                salt = salt.split('|')[2]
            salt = decodebytes(b(salt))
        assert len(salt) == sha1().digest_size
        hmac = HMAC(salt, b(hostname), sha1).digest()
        hostkey = '|1|%s|%s' % (u(encodebytes(salt)), u(encodebytes(hmac)))
        return hostkey.replace('\n', '')