apt.py: use subprocess.run with check=True instead of check_call when capturing stdout and stderr

[Perfect5th]

It's inadvisable to use check_call with stdout=PIPE and stderr=PIPE, as the child process will block if enough output is generated (see Note in https://docs.python.org/3/library/subprocess.html#subprocess.check_call)

We've seen some hanging subprocesses in the landscape-server charm due to this (and other, already addressed issues): https://bugs.launchpad.net/landscape/+bug/2033091

This change uses subprocess.run instead, with capture_output=True and check=True. Behaviour should be the same, except avoiding the aforementioned blocking issue.

[tonyandrewmeyer]

Thanks, LGTM!

[benhoyt]

Thanks! Changes look good to me, however, we need to bump up the LIBPATCH version here:

operator-libs-linux/lib/charms/operator_libs_linux/v0/apt.py

Line 125 in a1b80b3

LIBPATCH = 11

[benhoyt]

Excellent, thanks! subprocess.run is nice!

[benhoyt]

Separately, I've noticed that we're using e.output (stdout) in the exception messages, meaning that the actual error message doesn't get included in the output here, it just says "None". See #113. We'll fix that separately.

[benhoyt]

That said, @Perfect5th, if you would like to submit a PR to use e.stderr in those exceptions, go ahead. :-)

(I notice that this change will mean that e.output is b'' instead of None, but that doesn't help much.)