>      hs = mksrv(-1, 0, 443, u"special")

cls = <class 'dns.rdtypes.IN.SRV.SRV'>, value = -1

    @classmethod
    def _as_uint16(cls, value):
        if not isinstance(value, int):
            raise ValueError('not an integer')
        if value < 0 or value > 65535:
>           raise ValueError('not a uint16')
E           ValueError: not a uint16

../dns/rdata.py:385: ValueError

<DNS IN SRV rdata: -1 0 443 special.>