APT doesn’t resolve versions of packages based on requirements, but rather based on availability (and priorities). Put another way, it is really designed to work with coherent repositories, i.e. repositories with single versions of packages, where all related packages can be installed with the versions in the repository. (That’s how the Debian repositories ...
Aha, I was running systemctl daemon-reload but this wasn't enough. I needed to re-enable the child systemd unit in order to create the right set of symlinks.
$ systemctl reenable /etc/systemd/user/child.service
Created symlink /etc/systemd/system/multi-user.target.wants/child.service → /etc/systemd/user/child.service.
Created symlink /etc/systemd/system/...
Probably your package Database-devel provides Database-devel. You can check this like this:
rpm -q Database-devel --provides
it should say something like this:
Database-devel = 2.0.0-0
if it says also:
without version number, then this means for rpm and thus for yum that it provides all versions of Database-devel, including version 1.0.0....
For those who are still stuck on reinstalling Python3 after doing some unholy (to Debian) removal of Python3 (and not using the apt-get remove python3 correctly, I offer this 100% recovery step.