Comment 28 for bug 1895192

Thank you for the fcp install log. Here is the relevant excerpt, that clearly shows the error:

[...]
return volume path /dev/mapper/mpatha-part2
Checking if zkey encryption is supported...
Skipping kernel module load, pkey already loaded
Running command ['zkey', 'generate', '/tmp/tmp5ortqgw5'] with allowed return codes [0] (capture=True)
zkey encryption supported.
Attempting to setup zkey for None:dm_crypt-0
Running command ['zkey', 'generate', '--xts', '--volume-type', 'luks2', '--sector-size', '4096', '--name', 'dm_crypt-0', '--description', 'curtin generated zkey for None:dm_crypt-0', '--volumes', 'None:dm_crypt-0'] with allowed return codes [0] (capture=True)
Unexpected error while running command.
Command: ['zkey', 'generate', '--xts', '--volume-type', 'luks2', '--sector-size', '4096', '--name', 'dm_crypt-0', '--description', 'curtin generated zkey for None:dm_crypt-0', '--volumes', 'None:dm_crypt-0']
Exit code: 1
Reason: -
Stdout: ''
Stderr: zkey: Volume 'None' is not a block device or is not available

Traceback (most recent call last):
  File "/snap/subiquity/2499/lib/python3.6/site-packages/curtin/commands/block_meta.py", line 1445, in dm_crypt_handler
    util.subp(gen_cmd, capture=True)
  File "/snap/subiquity/2499/lib/python3.6/site-packages/curtin/util.py", line 275, in subp
    return _subp(*args, **kwargs)
  File "/snap/subiquity/2499/lib/python3.6/site-packages/curtin/util.py", line 141, in _subp
    cmd=args)
curtin.util.ProcessExecutionError: Unexpected error while running command.
Command: ['zkey', 'generate', '--xts', '--volume-type', 'luks2', '--sector-size', '4096', '--name', 'dm_crypt-0', '--description', 'curtin generated zkey for None:dm_crypt-0', '--volumes', 'None:dm_crypt-0']
Exit code: 1
Reason: -
Stdout: ''
Stderr: zkey: Volume 'None' is not a block device or is not available

Setup of zkey on /dev/mapper/mpatha-part2 failed, fallback to cryptsetup.
[...]

I've created another MP (https://code.launchpad.net/~slyon/curtin/+git/curtin/+ref/slyon/lp1895192-zkey) that should fix this issue.
@mwhudson: let me know what you think of that.
@fheimes: Could you give this other MP another test on real hardware? (i.e. by also scp'ing and bind-mounting the curtin/block/__init__.py file)