Migrate from distutils to setuptools

[alkisg]

Goal

In this issue we'll track how to move forward considering the intltool and distutils deprecations.

• GNOME recommends to migrate from Intltool to Gettext.
• PEP632 mentions that distutils is deprecated and applications should instead move to setuptools.
• PEP517 recommends pyproject.toml.
• This doesn't mean that setup.py is deprecated though, we just must not call it directly.
• But setuptools did deprecate data_files.
• Poetry suggests that applications shouldn't use sdists/wheels but e.g. apt/deb.
• Flit has limited support for external data.

So there's clear indication that the new python packaging tools are more oriented to cross-platform modules and less appropriate for OS-specific things like man pages, desktop files, systemd services, xdg autostarted scripts, translations etc. These things still need a setup.py or a makefile.

Let's assume that epoptes (GUI), epoptes-client and epoptesd (twisted) were cross-platform applications that could run in any OS (assuming all prerequisites like GTK and twisted are installed). These modules could use the modern tools and declare package data for things like glade.ui files or icon.svg files.

Proposed changes

# Regenerate POTFILES.in:
find .. -name '*.ui' -or -name '*.py' | sed 's|^[^/]*/||' | LANG=C sort >POTFILES.in

# Regenerate epoptes.pot:
xgettext --add-comments --directory=.. --default-domain=epoptes --output=epoptes.pot POTFILES.in

# The .po files are periodically downloaded from launchpad

TODO:

• Handle ../data/epoptes.desktop.in while avoiding X-Ubuntu-Gettext-Domain=epoptes.
• Update license identifiers to spdx
• Translations should probably be included as package data by setuptools. While if deb/rpm are used, they could move them to global locations.