Comment 5 for bug 1640523

This isn't a bug in ubuntu-image. The crash is coming from `snap prepare-image` and u-i just forwards that along because there's nothing more it can do. I opened a bugtask for snapd; here's how to reproduce it.

1. wget the model and the gadget snap from w-ondra's attachements
2. ubuntu-image --channel edge -o ../images/ondra.img -d ../models/pi3-ondra.model --extra-snap ../ondra/pi3-ondra_16.04-0.5_armhf.snap

Here's the full traceback so you can see it's coming from snap.

DEBUG:ubuntu-image:-> [ 0] make_temporary_directories
DEBUG:ubuntu-image:-> [ 1] prepare_image
error: attribute "usb-vendor" of slot "zwave-aeon-g5": invalid attribute scalar: 658
ERROR:ubuntu-image:COMMAND FAILED: snap prepare-image --channel=edge --extra-snaps=../ondra/pi3-ondra_16.04-0.5_armhf.snap ../models/pi3-ondra.model /tmp/tmpsbngmcs_/unpack
ERROR:ubuntu-image:Full debug traceback follows
Traceback (most recent call last):
  File "/home/barry/projects/ubuntu/allsnappy/ubuntu-image/ubuntu_image/builder.py", line 128, in prepare_image
    self.args.channel, self.args.extra_snaps)
  File "/home/barry/projects/ubuntu/allsnappy/ubuntu-image/ubuntu_image/helpers.py", line 116, in snap
    run(cmd, stdout=None, stderr=None, env=os.environ)
  File "/home/barry/projects/ubuntu/allsnappy/ubuntu-image/ubuntu_image/helpers.py", line 97, in run
    proc.check_returncode()
  File "/usr/lib/python3.5/subprocess.py", line 659, in check_returncode
    self.stderr)
subprocess.CalledProcessError: Command '['snap', 'prepare-image', '--channel=edge', '--extra-snaps=../ondra/pi3-ondra_16.04-0.5_armhf.snap', '../models/pi3-ondra.model', '/tmp/tmpsbngmcs_/unpack']' returned non-zero exit status 1