bpo-29535: Not all datetime objects are using hashing randomization

[arigo]

Security concern: pending feedback on issue bpo-29535, here is an update of the documentation. It should make it clear that not all datetime objects come with randomized hashes.

https://bugs.python.org/issue29535

[mention-bot]

@arigo, thanks for your PR! By analyzing the history of the files in this pull request, we identified @tiran, @birkenfeld and @ncoghlan to be potential reviewers.

[abalkin]

It is not clear what "some datetime objects" include. Is it some subset of date, time, datetime, timezone types or some instances of these types get randomized hash and some don't? If we are going to document the current implementation we should explain precisely which objects have deterministic hash and which don't.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

And if you don't make the requested changes, you will be put in the comfy chair!

[arigo]

Closing. I tried to get an important security detail into the docs quickly, because bpo-29535 was not going to be fixed soon. I was right about that, but wrong about this doc fix---it was also not going to be accepted quickly. There is no point then.