Booting into rescue mode fails when mounting file systems on /mnt/sysimage.

Issue

• Booting into rescue mode with RHEL 8.2 or an earlier ISO fails when trying to mount the file systems on /mnt/sysimage, gets a python traceback, and then "Pane is dead" :

The rescue environment will now attempt to find your Linux installation and mount it under the directory: /mnt/sysroot/. You can then make any changes required to your system. Choose 1 to proceed with this step. You can choose to mount your file systems read-only instead of read-write by choosing 2. If for some reason this process does not work choose 3 to skip directly to a shell.

1) Continue
2) Read-only mount
3) Skip to shell
4) Quit (Reboot)
Please make a selection from the above: 1
...snip...
TypeError: unsupported operand type(s) for +: 'method' and 'list' 
...snip...
Pane is dead