python3 compatibility

[mengesb]

Python 2.x is getting a little old and Python 3 is the way forward. I've personally updated the code base using the 2to3 conversion tool which made relatively minor updates; perhaps this is a quick way forward.

[lanky]

might well work. Family and work commitments mean I don't have that much time to work on any of this (we also don't use spacewalk here). While python2 is getting a little old, it's still in widespread use (and the default on most Enterprise Linux OSes) so I'm not quite ready to deprecate it completely.
Probably a good idea to support it as much as we can as long as backwards compatible.