gzip.compress output is non-deterministic

[bmwiedemann]

Bug report

Bug description:

import gzip
gzip.compress(b'')

output varies by default, which breaks reproducible builds in cases such as
https://github.com/getmoto/moto/blob/fc60bd1c5f6e6184e30a6db8b65059a2855cd28e/setup.py#L28

GNU gzip (since 1.10) defaults to a zero timestamp for compressing stdin. And after year 2106, no mtime could be stored anyway.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-125260: gzip: let compress mtime default to 0 #125261

[ZeroIntensity]

Per @AA-Turner, I'm marking this as a feature.