We disabled this entirely for bug 447808, but I think it makes sense to re-enable it by default. We just need to provide a way for ebuilds to disable it in the eclass so they can handle it more precisely when python is an optional feature.
I think a nice compromise would be to enable it by default in distutils-r1, with an option to disable it with the DISTUTILS_OPTIONAL variable. We could then require ebuilds which use python-r1 directly to set REQUIRED_USE themselves, just as they do with PYTHON_DEPS in DEPEND.
I see one major problem here. We need to find a non-confusing name. And considering that we use PYTHON_REQ_USE for something completely different doesn't help.
Yes, that is unfortunate. Perhaps we could deprecate the PYTHON_REQ_USE variable and rename it to something else. Then, we could use a name like PYTHON_REQUIRED_USE for exporting metadata without causing too much long-term confusion.
+ 21 May 2013; Mike Gilbert <floppym@gentoo.org> distutils-r1.eclass, + python-r1.eclass, python-single-r1.eclass: + Set PYTHON_REQUIRED_USE, and add it to REQUIRED_USE in distutils-r1.
