Comment 5 for bug 1855013

Hit this today on juju 2.9.27, Bionic => Focal. On the "complete" step after the upgrade two subordinates got stuck with 'hook failed: "post-series-upgrade"', apparently while resuming services like this:

2022-06-16 02:32:06 WARNING unit.ceilometer-agent/4.post-series-upgrade logger.go:60 raise Exception("Couldn't resume: {}".format("; ".join(messages)))
2022-06-16 02:32:06 WARNING unit.ceilometer-agent/4.post-series-upgrade logger.go:60 Exception: Couldn't resume: ceilometer-agent-compute didn't resume cleanly.; Services not running that should be: ceilometer-agent-compute
2022-06-16 02:32:06 ERROR juju.worker.uniter.operation runhook.go:146 hook "post-series-upgrade" (via explicit, bespoke hook script) failed: exit status 1

However I was able to systemctl start the services without issues. Looks like juju never retried it or checked again and remained stuck.