Comment 6 for bug 1802304

When I encountered this just now with 21.04 charms, it appears that the real resolution is that update-alternatives switches privsep-helper from py2 to py3 when you purge the python-oslo.privsep package.

Suggest that the python3-oslo.privsep package in UCA:bionic-rocky should force update-alternatives.

I see that python-oslo.privsep is prevented from being removed by the charm because python-os-brick relies on it.