Code review comment for lp://staging/~rvb/maas/dhcp-stop-bug-1328656

> Also I'd at least normalise whitespace:
> ' '.join(output.strip().split()). It may even be worth a dedicated test.

Why do you think this is worth the trouble? I mean, this error string is present in upstart's source code.

> You may also want to say that (apparently) the error ends in a colon, with
> nothing to follow. It looks weird, and reading it I sort of expected a
> "message begins with" check.

I know it looks weird, but that's what the error looks like. I could relax the condition a bit (by just checking that the error contains "Unknown instance") but I think it's much more important not to hide legitimate errors so I'd rather keep a very precise check. The worse that can happen is that the user will see misleading stacktraces: painful but not as misleading as missing valid errors.