Fixed #23321 -- Generated .mo files at setup time

[claudep]

No description provided.

[claudep]

In this new version, only the sdist command is always compiling .mo files. Otherwise, python setup.py build_mo can be run to manually compile mo files. We could then even remove the trans_real.py addition of this patch and add the python setup.py build_mo instruction in the documentation at proper places.

[timgraham]

Code looks fine to me, but someone with experience with translations should offer an opinion on your comment. Is this change transparent to users running with a development version of Django or are some release notes required?

[claudep]

Currently, it should be transparent due to the check added in trans_real.py. But I'm not yet sure it's the right thing to do. This adds a small overhead to every translation setup. The alternative would be to document the need to run python setup.py build_mo when running with a checked-out Django version. More opinions welcome.

[timgraham]

@jezdez, as former translation manager maybe you could offer an opinion on this?

[jezdez]

I've marked the ticket as Someday/Maybe on the grounds of this patch not being optimal. If we could somehow get rid of the dependency on the gettext library (e.g. via Babel) that would solve the problem.