bpo-32417: Make timedelta arithmetic respect subclasses (#10902)
* Make timedelta return subclass types
Previously timedelta would always return the `date` and `datetime`
types, regardless of what it is added to. This makes it return
an object of the type it was added to.
* Add tests for timedelta arithmetic on subclasses
* Make pure python timedelta return subclass types
* Add test for fromtimestamp with tz argument
* Add tests for subclass behavior in now
* Add news entry.
Fixes:
bpo-32417
bpo-35364
* More descriptive variable names in tests
Addresses Victor's comments
4 files changed