The wiki here is based on Pywiki 0.4.2. It's been a great wiki for this site. Here is a patch with some modifications I've made to it. I hope you'll think they are improvements. The changes are described below.
Pywiki had a few HTML goofs in it. I've added HTML validity checking to all of the tests that generate HTML. The unit tests now require the WDG html validator. The code changes were pretty simple. I did get defeated in the page formatter, where I ended up shrugging my shoulders and inserting an ugly hack to cause <p> tags to be outside of certain sections (most notably <pre></pre>).
Pywiki used some deprecated features in Python that were finally removed in Python 2.1. I noticed this when a routine upgrade of the server caused the search feature to break. One of the problems was that list.append no longer takes multiple arguments and turns them into a tuple for you. The other problem is that one of the modules started complaining that it didn't know what the "sys" module was anymore. I added an "import sys" to it and the problem went away. I can only guess that "sys" was being imported implicitly and some language change changed that.