[Python-ideas] Make it optional

[Stephen J. Turnbull]

anatoly techtonik writes:

 > PEPs are made to resolve ambiguities. But it doesn't mean
 > limiting flexibility and setting hard limitation. What is hard
 > limitation standard? For example, marking version you can
 > not parse as pre-release. PIP actually does this, which
 > prevents all packages with versions that are not comply with
 > "versioning PEP" from installing.

You say you've filed a bug.  That's the right thing to do.  AFAICT, to
the extent that it really *prevents* installation, it doesn't conform
to PEP 440 (see "Handling of Pre-Releases" and "Direct References" in
the PEP).  Since it is arguably a bug, it doesn't need discussion
here.