[Distutils] PEP 345, 566, 508 version specifiers and OR clauses

[Barry Warsaw]

I'm about to release a new version of importlib_resources, so I want to
get my flit.ini's require-python clause right.  We support Python 2.7,
and 3.4 and beyond.  This makes me sad:

requires-python = '>=2.7,!=3.0,!=3.1,!=3.2,!=3.3'

Of course, I'd like to write this like:

requires-python = '(>=2.7 and <3) or >= 3.4'

I understand that OR clauses aren't supported under any syntax
currently, but as PEPs 566 and 508 are still open/active, wouldn't it be
reasonable to support something like this explicitly?

It seems like wanting to support 2.7 and some versions of Python 3 (but
not all) is a fairly common need.

Cheers,
-Barry