Wow, that was quick… It is a bit unfortunate that this has crept in right before the release. I hope that there are not too many Trac users who still run on Python 2.3.
Anyway, it's fixed in 0.11-stable in [7667]. Thanks for the bug report. Did you have any other problems with 0.11.2 related to Python 2.3? Ideally, we should have a 2.3 build host for 0.11-stable, but I think this will be difficult.
What's the policy for such a "blocker" issue (for 2.3)? Should we tell people to install from SVN, or do we re-tag and update the release tarballs?