Bug#933523: Possible solution
On Wed, 2021-07-21 at 12:51 +0200, John Paul Adrian Glaubitz wrote:
> Are you seeing any log messages indicating that mountvirtfs() failed
> during the installation of the grub-installer udeb?
So *that*'s what the postinst file is for! ;-)
No, I see no messages indicating any errors. I just double-checked by
monitoring `tail -f /var/log/syslog | grep efivars` during installation.
I did see a debug message I added right before the call to mountvirtfs
but no error message.
Also, if I understand correctly, in case of an error the script would
`exit 1` and the installation process would stop.