Comment 2 for bug 1769191

Since you've marked this invalid, just to check on the underlying issue, what happens now if the version of checkbox-ng on the target is different than the local?

Originally that caused the confusing, unhelpful tracebacks I saw, and I can see it being possible that this could happen routinely, especially if, for example, your local system is using checkbox-ng from stable while your test machine is using checkbox-ng from dev.