unhelpful failure message

[Casper]

see https://github.com/casperdcl/cdcl/runs/447883745#step:6:20

The output is very unhelpful; doesn't actually say what the error was.

Preparing to push 'gh_0.5.5-pre.1-55-gd7181b1_amd64.snap'.
After pushing, the resulting snap revision will be released to 'edge' when it passes the Snap Store review.
Running the review tools before pushing this snap to the Snap Store.
Sorry, an error occurred in Snapcraft:
Command '['/snap/bin/review-tools.snap-review', '/home/runner/work/cdcl/cdcl/cli/gh_0.5.5-pre.1-55-gd7181b1_amd64.snap', '--json']' returned non-zero exit status 1.
Traceback (most recent call last):
  File "/snap/snapcraft/3970/bin/snapcraft", line 11, in <module>
    load_entry_point('snapcraft==3.9.1', 'console_scripts', 'snapcraft')()
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/snapcraft/cli/store.py", line 176, in push
    review_snap(snap_file=snap_file)
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/snapcraft/cli/_review.py", line 33, in review_snap
    review_tools.run(snap_filename=snap_file)
  File "/snap/snapcraft/3970/lib/python3.6/site-packages/snapcraft/internal/review_tools/_runner.py", line 38, in run
    subprocess.check_output(command, stderr=subprocess.STDOUT, env=env)
  File "/snap/snapcraft/3970/usr/lib/python3.6/subprocess.py", line 356, in check_output
    **kwargs).stdout
  File "/snap/snapcraft/3970/usr/lib/python3.6/subprocess.py", line 438, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['/snap/bin/review-tools.snap-review', '/home/runner/work/cdcl/cdcl/cli/gh_0.5.5-pre.1-55-gd7181b1_amd64.snap', '--json']' returned non-zero exit status 1.
You can find the traceback in file '/tmp/tmpwvm3sl16/trace.txt'.
##[error]Process completed with exit code 1.

[Jamie Strandboge (jdstrand)]

Thank you for reporting a bug. There may indeed be a review-tools bug, but the UI issue appears to be in snapcraft.