1. Updating Python
If you want to change the Python running your MoinMoin installation there are some issues to keep in mind:
1.1. Location of the MoinMoin directory
The default installation process (setup.py) installed the MoinMoin files into the site-packages directory of the current Python installation (for example /usr/lib/python2.4/site-packages). If you move to another Python interpreter you must reinstall the MoinMoin files into the new lib/pythonX.X/site-packages directory. If you installed the MoinMoin files elsewhere and adjusted sys.path this is not a problem.
1.2. The precompiled Python files (.pyc)
Python does not grant that .pyc files are compatible between Python versions. If you change the Python interpreter you should recompile the Python scripts. You may use
python -c "import compileall; compileall.compile_dir('/path/to/MoinMoin')"
for this. If you reinstall MoinMoin for the new interpreter the step is not needed/done by setup.py.
1.3. Empty Page Cache
The page cache uses Python byte code for faster page rendering. To avoid compatibility problems you should empty the cache by hand by deleting all files in data/pages/*/cache/ and underlay/pages/*/cache/.