However, as we are days away from the end-of-life cliff for the operating system as a whole, and as I discovered a few minutes ago, dozens of packages are already unsupported and not receiving security updates, I'm going to upgrade the host OS manually, even if it results in some disruption.  As with the Twisted compatibility policy, security is a good enough reason to break stuff.

Maybe we'll even get a new version of Mailman that will let me turn automatic subscriptions back on while the star-crossed https://lists.twistedmatrix.com project waits for someone else to help out :-).