Avoid crash when closing a already closed circuit

Closes tails#20003

See merge request !8

FWIW it actually doesn't break anything.

Remove deprecated functions

See merge request !7

Replicate Vidalia's ability to close arbitrary circuits

See merge request !6

Allow copying relay information

See merge request !5

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