sys._current_exceptions() should return exceptions rather than exc_info tuples

[iritkatriel]

The function sys._current_exceptions() returns a mapping of thread-id to an exc_info tuple representing that thread's handled exception. As part of the larger effort of moving away from exc_info to simple exception instances, we should change this mapping to have just the exception instance as value.

While this is a breaking change, I think we can do this without a deprecation period because this function is named with a leading _, and it is documented as "for internal and specialized purposes only".

Linked PRs

• gh-103176: sys._current_exceptions() returns mapping to exception instances instead of exc_info tuples #103177

[iritkatriel]

Marking as blocker so we won't forget to make a decision about whether this should be done via a deprecation cycle (it's not really a blocker, the label can be removed).