Lloyd had posted a comment asking what I knew of/thought of this Zope-based CMS system – Plone.
I went and had a quick look today. As I mentioned, it is built on top of Zope, which is itself a server/development environment/lots of other things that is written in Python.
I imagine Plone has lots of the same benefits as Zope – object-oriented, built-in management of permissions/roles for users and groups, etc., as well as the same drawbacks – must be run on top of Zope, steep learning curve, low availability of skilled Python/Zope developers.