What were you trying to do that didn't work?

Perform Leapp IPU from RHEL 7 to RHEL 8 with grub2-pc-modules package removed from system

Please provide the package NVR for which bug is seen:

leapp-0.16.0-1.el7_9.noarch

How reproducible:

100%

Steps to reproduce

Remove grub2-pc-modules package

1. rpm -e grub2 --justdb
2. rpm -e grub2-pc-modules grub2-pc --justdb

Proceed with leapp upgrade.
Reboot

Expected results

Leapp should inhibit if grub2-pc-modules package is not listed installed in rpmdb

Actual results

Leapp doesn't detect this and shows no inhibitor
System ends up in a grub> post successful leapp upgrade.

Addition information

With RHEL 8 we have introduced blscfg which is incorporated inside grub.cfg
~~~
insmod blscfg
blscfg
~~~

There is a module that's needed by grub to work with blscfg `/boot/grub2/i386-pc/blscfg.mod` (increment.mod doesn't actually block using blscfg as per more in-depth reproducers confirmed but missing blscfg.mod is more problematic ).

This module is provided by package grub2-pc-modules of el8 version and is not present in el7 version of the package.
Since this package is not listed as installed leapp doesn't install el8 version and increment.mod is never added into system on /usr/lib/grub/i386-pc path .
And grub2-install never pulls it in /boot/grub2/i386-pc path for grub to use during booting
Hence we end up with grub> with no visible error.

To be able to see this error the only way that exists is to load the config file within grub prompt

grub> configfile (hd0,msdos1)/grub2/grub.cfg
error: file '/grub2/i386-pc/increment.mod' not found
error: can't find command 'blscfg'.

This makes it very difficult to troubleshoot this issue.