The only production-quality python-based CMSes are those in the ["Zope"] world such as [http://www.plone.org Plone].
For those wanting lighterweight non-Zope CMS solutions, there are very few options and apparently those are works in progress. If you are happy to code and send patches, you might want to look at the following, otherwise stick with Plone and its Zope-based cousins.
There is the [http://www.divmod.org/Home/Projects/Nevow/index.html Nevow]-based [http://svn.twistedmatrix.com/cvs/trunk/?root=Payago Payago, a lightweight website management system] whose predecessor is [http://mesozoic.geecs.org/devel/go/ Go, an application for developing Woven-based web sites]
For ["Webware"] there is the [http://cvs.sourceforge.net/viewcvs.py/webware-sandbox/Sandbox/fbar/teeny_tiny_cms/ teeny_tiny_cms] which uses SQLObject, SQLite and Docutils
And for some applications, you maybe want to use a wiki (a very simple sort of CMS), like MoinMoin (this is what is used right here).