I keep running into problems caused by stale installations from the AUR,
such as upgraded, ABI-incompatible dependencies or Python packages still
installed under /usr/lib/python3.5/ where they are no longer found since
the move to python3.6.
My understanding is that in such situations, the affected packages
should bump pkgrel to force rebuild and reinstall, even if the source
and the rest of the PKGBUILD remain unchanged.
Is this understanding correct? If so, can this be clarified in places
such as  where people cannot miss it?
Confronted with this issue, some maintainers advise their users to just
rebuild by hand, but that defeats part of the purpose of package
management systems. I don't want to have to debug weird run-time errors
one by one, trace the problem to this trivial issue, and then solve each
of them by manual rebuild.