It's not 10.1 problem, our RPM upgrade from one major version to another does not work in general, and AFAIR never has. It's been discussed, but since I can't find an open JIRA issue, assigning to serg to decide if we want to do something about it now.

Actually, I think we might. We're supposed to be good at upward compatibility. Downstream packages certainly allow upgrades (just checked mariadb-server from FC24).

And we test upgrades in buildbot, aren't we?
So, let's remove this check.

Actually, we don't test major upgrades now in buildbot – we do for debs, but not for RPMs – exactly because it made no sense, as it was disabled. But that's not a good reason not to support it, I'll see if I can make it work with existing VM images (for debs we have special images with pre-installed MariaDB or MySQL for upgrade tests).

MySQL supports major upgrades too btw – I think they used not to, but yesterday I ran 5.6=>5.7 and it worked.

For now, I've filed everything that my tests revealed.

created documentation issue DOCSCOLLAB-1371