Quoting Luca Falavigna <ftpmaster at ftp-master.debian.org>:
> python{,3}-cheetah and python{,3}-flup do not exist in archive, but
> they're listed in Recommends.
> Wouldn't it make sense to drop them until they're packaged?
Yes! This was an oversight on my side.
Thanks for spotting it, Luca!