Message 299222 - Python tracker

Ok, I merged the change in the 3.6 branch.

I decided to not merge the 3.5 change, since it's now too late: 3.5 slowly enters a new security-only fixes:
https://github.com/python/cpython/pull/2815

Thanks Utkarsh Upadhyay for your work on datetime, not only this issue, but also repr(timedelta) (and maybe also timedelta constructor doc later? ;-)).