Fail instead of warn for unsigned lines in InRelease

The warnings were introduced 2 years ago without any reports from the
wild about them actually appearing for anyone, so now seems to be an as
good time as any to switch them to errors.

This allows rewritting the code by failing earlier instead of trying to
keep going which makes the diff a bit hard to follow but should help
simplifying reasoning about it.

References: 6376dfb8dfb99b9d182c2fb13aa34b2ac89805e3

0 files changed, 0 insertions, 0 deletions