2.6.X appears to work great with Python 2.2. We even removed the startup warning lately. I'd go this way were I you as 2.7 is probably still some time away and you almost certainly don't want to be tracking the trunk, as its relatively volatile at the moment.
I run 2.6.1 with Python 2.2.2 with several additional products without any problems. I learnt my lessons from upgrading to early major releases of Zope, so I would go for 2.6.1 with Python 2.2.2 instead of waiting for a (maybe) buggy release of 2.7.0...
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