With Python's PEP 517, Python democratized the build system for python modules, allow anyone to create their own build system and others to leverage it by referencing it in a 'pyproject.toml' file. Flit (https://flit.pypa.io/en/latest/) is one such build system, and it is currently used by typing-extensions (see FL-9074). In this bug, we locked typing-extensions to a 3.x version that still works with setuptools.

But twine (python package uploader, see FL-9616) now needs a package called "rich", which in turn needs typing-extensions 4 or later, so in order for me to fix twine (FL-9616), I must first fix FL-9074, and before I can do that, we need flit.

So this bug represents that task.

Now, once flit is added, we should try to use it to create the rich dependency for twine, thus fixing FL-9616. But Gentoo has some new distutils-r1.eclass support for these new build systems. I don't know if I like it, but I have also not tried messing with flit. We should try to add flit and then see how involved it is to use flit to build rich. Because we might be able to add it as a dep and then just call the right thing and away we go, we're usin' flit.