gzip compression, using class GzipFile from gzip.py, by default inserts a timestamp to the compressed stream. If the optional argument `mtime` is absent or None, then the current time is used .
This makes outputs non-deterministic, which can badly confuse unsuspecting users: If you run "diff" over two outputs to see whether they are unaffected by changes in your application, then you would not expect that the *.gz binaries differ just because they were created at different times.
I'd propose to introduce a new constant `NO_TIMESTAMP` as possible value of `mtime`.
Furthermore, if policy about API changes allows, I'd suggest that `NO_TIMESTAMP` become the new default value for `mtime`.
How to proceed from here? Is this the kind of proposals that has to go through a PEP?