Comment 8 for bug 1905412

I today received a note from an IBMer who had issues to (re-)install an IBM Z system with various DASD ECKD disks in a LVM configuration.
I was able to recreate the situation on our system and itis as follows:

more than 2 DASDs (used 8 DASD mod3) with:
dasda1 0.75 GB for /boot
dasda2 rest for a lvm vg
all other DASD entirely for that same vg
and a single lv with entire space on top of that vg as root

1) running this installation with pristine DASDs (never low-level formatted before) works fine
2) re-running that installation and only slightly changing the config of dasda (doing a reformat and defining /boot with .5GB, rest for the vg) makes the installer to fail
3) re-running that installation and reformatting ALL disk (and defining them with dasda1 /boot 0.5GB and rest in vg like before) works again

case 2) shows:

 Verifying /dev/dasdc part 1 size, expecting 50027 tracks, found 50027 tracks
 /dev/dasdc partition 1 already present, skipping create
 An error occured handling 'partition-dasdc1': UnboundLocalError - local variable 'part_path' referenced before assignment
 finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: configuring partition: partition-dasdc1
 TIMED BLOCK_META: 5.790
 finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: curtin command block-meta
 Traceback (most recent call last):
   File "/snap/subiquity/2364/lib/python3.6/site-packages/curtin/commands/main.py", line 202, in main
     ret = args.func(args)
   File "/snap/subiquity/2364/lib/python3.6/site-packages/curtin/log.py", line 97, in wrapper
     return log_time("TIMED %s: " % msg, func, *args, **kwargs)
   File "/snap/subiquity/2364/lib/python3.6/site-packages/curtin/log.py", line 79, in log_time
     return func(*args, **kwargs)
   File "/snap/subiquity/2364/lib/python3.6/site-packages/curtin/commands/block_meta.py", line 111, in block_meta
     return meta_custom(args)
   File "/snap/subiquity/2364/lib/python3.6/site-packages/curtin/commands/block_meta.py", line 1935, in meta_custom
     handler(command, storage_config_dict)
   File "/snap/subiquity/2364/lib/python3.6/site-packages/curtin/commands/block_meta.py", line 974, in partition_handler
     LOG.debug('Wiping partition %s mode=%s', part_path, wipe_mode)
 UnboundLocalError: local variable 'part_path' referenced before assignment
 local variable 'part_path' referenced before assignment
 curtin: Installation failed with exception: Unexpected error while running command.
 Command: ['curtin', 'block-meta', 'simple']
 Exit code: 3

This msg is different to the one in the bug description here, but I've added this case here, since the situation is very similar.

(importance is probably 'Medium', since a workaround is to reformat all in case of a modified re-install)

And btw. a 21.04 daily was used (timestamp Apr 12th)