curtin custom install fails with spare unused disk

[Ryan Harper]

[ 52.809564] cloud-init[931]: An error occured handling 'vdb': UnboundLocalError - local variable 'ptuuid' referenced before assignment
[ 52.816943] cloud-init[931]: local variable 'ptuuid' referenced before assignment
[ 52.836756] cloud-init[931]: Installation failed with exception: Unexpected error while running command.
[ 52.838824] cloud-init[931]: Command: ['curtin', 'block-meta', 'simple']

storage.cfg

storage:
    version: 1
    config:
    - id: vda
        type: disk
        ptable: msdos
        path: /dev/vdc
        name: vda
        wipe: superblock
        grub_device: true
    - device: vda
        id: vda-part1
        name: vda-part1
        number: 1
        offset: 2097152B
        size: 17176723456B
        type: partition
        uuid: d9a3d0e8-1a4c-4b62-a666-286902f7ffd8
        wipe: superblock
    - fstype: ext4
        id: vda-part1_format
        label: root
        type: format
        uuid: 22c010b5-bcfd-40cc-9f96-cefa1bcf7c64
        volume: vda-part1
    - device: vda-part1_format
        id: vda-part1_mount
        path: /
        type: mount
    - id: vdb
        type: disk
        path: /dev/vdd
        name: sparedisk
        wipe: superblock

[Ryan Harper (raharper)]

Workaround is to apply a partition table to the disk.

ptable: gtp | ptable: msdos

[Scott Moser (smoser)]

This bug is believed to be fixed in curtin in 17.1. If this is still a problem for you, please make a comment and set the state back to New

Thank you.