IPv6 host address processing broken

[GoogleCodeExporter]

This is a bug report forwarded from Debian, see 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=741537

If possible, include [email protected] in the correspondence.

The handling of IPv6 addresses is broken since the ``parse_host_entry()``
function in ``psshutil.py`` thinks the colons in it are an indication for a
port and the last component is taken apart.  Enclosing the address in brackets
doesn't work either because the host name resolution includes the brackets
around the IP address.

(A workaround is sticking a ``:22`` at the end of addresses with no port, but
it results in non-standard addresses.)

pssh should at least allow to specify IPv6 addresses enclosed in brackets
(ideally without brackets if no port is specified).  IPv6 addresses can be
identified with a proper regular expression or because they have at least
two colons.

Original issue reported on code.google.com by [email protected] on 12 May 2014 at 12:08