On Tuesday, 19 February 2013, M.-A. Lemburg wrote:
The only tool in wide spread use that understands part of the 1.2 data
is setuptools/distribute, but it can only understand the Requires-Dist
field of that version of the spec (only because the 1.1 Requires field was
deprecated) and interprets a Provides-Extra field which isn't
even standard. All other 1.2 fields are ignored.
setuptools/distribute still writes 1.1 meta-data.
I've never seen environment markers being used or supported
in the wild.
I'm not against modernizing the format, but given that version 1.2
has been out for around 8 years now, without much following,
I think we need to make the implementation bit a requirement
before accepting the PEP.