Bug#873520: lintian: Check for bad-distribution in debian/changelog too

[Jeremy Bicha <jbicha@ubuntu.com>]

Source: lintian
Version: 2.5.52

I was surprised to see that pyjunitxml 0.6-1.2 was accepted into
Debian unstable with its debian/changelog still set to UNRELEASED. I
guess the uploader managed to generate a valid .changes file.

https://tracker.debian.org/news/859782

lintian already has a check for bad-distribution-in-changes-file

I request that a bad-distribution-in-debian-changelog check be added.

I think this would make a good candidate for dak auto-reject too.

Thanks,
Jeremy Bicha