refresh_package_versions() must skip binary blobs in debian/

system-image has a binary blob in its debian/ directory, specifically the archive-master.tar.xz keyring.

in packagemanager.py, refresh_package_versions(), it globs debian/* and then tries to open every file found there in utf-8 mode to do a version replacement. This fails on debian/archive-master.tar.xz (probably - it's hard to tell from the traceback, but it's the only candidate):

https://ci-train.ubuntu.com/job/ubuntu-landing-011-1-build/148/console

Two options that I see, one easy, one harder.

The easy option: just catch any UnicodeDecodeError that happens while reading data out of utf8_inplace(path), and assume the file is binary, so just skip it.

The problem with that is that you could potentially do a harmful string replacement in a binary blob that's accidentally utf-8 compatible.

The hard option: either whitelist the files in debian/* that you want to do the replace of (rather than just the glob of everything in debian/*) or find a way to blacklist certain files. The latter probably requires the package being built to specify that in some way, though I don't know where that would be (a d/control header? some magic debian/* file?). Besides, it's probably safer to whitelist anyway.