Juju on python 2.6

[Clint Byrum]

In my most recent attempts to get as broad a base of testing as possible,
I ran the test suite on Lucid.

The fails are here:

http://paste.ubuntu.com/705630/

Most of these are just simple 2.6 vs. 2.7 minor incompatibilities or a
few cases of updated API's being used.

Before I expend any energy on this, how interested are we in making
sure juju works on Python 2.6? I figure a jenkins slave running the test
suite on lucid will find most issues.

As a wrap up of other possible targets for juju clients:

Ubuntu Lucid:    2.6
Ubuntu Maverick: 2.6 default, 2.7 available
Ubuntu: Natty+:  2.7
Mac OS X Lion:   2.7
Fedora 15:       2.7
RHEL 6:          2.6

My personal feeling is that we should probably make sure the *client*
works on lucid, but not worry too much if the whole of the unit tests
fail.

If others agree, then I will modify the build scripts to not run the
unit tests on lucid and to require python 2.7 for maverick.