urlparse does not handle raw IPv6 address the way I though it does - extracted
hostname is not the whole address, but only the first part of it:

    In [3]: urllib.parse.urlparse('z://2a11:9ac1:6::5')
    Out[3]: ParseResult(scheme='z', netloc='2a11:9ac1:6::5', path='', params='', query='', fragment='')

    In [4]: _.hostname
    Out[4]: '2a11'

Tests did not noticed this because previouslt we had e.g 4321::1 in the
address, and netaddr thinks 4321 is valid ipv4 address:

    In [6]: netaddr.IPAddress('4321')
    Out[6]: IPAddress('0.0.16.225')

However changing IPv6 addresses to use hex letter trigger the bug with e.g.

       raise AddrFormatError('failed to detect a valid IP ' \
    netaddr.core.AddrFormatError: failed to detect a valid IP address from '2a11'

-> Fix it by avoiding urlparse and doing ip/port splitting ourselves by hand.

/reported-by @lu.xu