Make USES=python without argument mean 3.6+.

[mat]

Summary

This is getting us one step further to deorbitting Python 2.7.

[antoine]

The following ports have to be changed to unbreak bulk -a:

converters/py-webencodings
databases/py-sqlite3
devel/py-Jinja2
devel/py-babel
devel/py-future
devel/py-game_sdl2
devel/py-ply
devel/py-pycparser
devel/py-pytz
devel/py-setuptools
devel/py-setuptools_scm
devel/py-six
devel/py-subversion
devel/scons
dns/py-dnspython
lang/cython
misc/py-tqdm
textproc/py-markupsafe
textproc/py-pygments-25
textproc/py-toml
www/py-html5lib
x11-toolkits/py-tkinter

[mat]

• Make USES=python without argument mean 3.6+.
• Those ports are allowed to build a 2.7 flavor.

[mat]

In D28459#636793, @antoine wrote:

The following ports have to be changed to unbreak bulk -a:

Done.

[rene]

Mk/Uses/python.mk

340

It would also be a good idea to explain this change in the introducery comments at the start of this file.

[rene]

General question: how are we going to avoid people adding 2.7 support to a port because upstream still supports it?

[mat]

In D28459#636864, @rene wrote:

General question: how are we going to avoid people adding 2.7 support to a port because upstream still supports it?

I was contemplating a commit hook.

Or just saying something like DON'T DO IT, IF YOU DO, THE PORT WILL BE REMOVED. or something similar and kind.

[mat]

Fixup doc at the start of python.mk.