Make setuptools aware no packages/modules are shipped

See merge request tails/onioncircuits!4

Newer versions of setuptools will complain when no package names
are declared and will try to infer package names from the directory
layout, which fails since the repo contains other top-level directories
unrelated to packages. This change ensures that setuptools knows we are
shipping no packages.

Support closing the application with CTRL+q, minor code modernization

See merge request !2

Remove the "Published:" field

See merge request !1

Reference: https://wiki.gnome.org/Projects/PyGObject/InitializerDeprecations

Current stem raises DescriptorUnavailable in those cases so we can catch this
one, instead of the über-generic grand-parent OperationFailed exception.

https://stem.torproject.org/api/control.html#stem.control.Controller.get_network_status

On tails#15619 we realized that:

 - This field is not particularly useful: most users won't know what that info
   means, let alone what they can/should do with it.

 - In the current state of things, it lacks context for translators.

Let's remove it.

Closes tails#17846

Needed on recent Debian sid, as reported on Debian bug #865843.

The current best practice, to allow users to locally override AppArmor profiles
shipped as conffiles, is to source "/etc/apparmor.d/local/<profilename>" in
every profile. Then, dh-apparmor takes care of creating/removing this file in
maintainer scripts. The Debian packaging for onioncircuits already uses
dh-apparmor to manage that local override file, so all that's missing is
actually including it, which this commit does.