gh-146092: Raise MemoryError on allocation failure in _zoneinfo

[vstinner]

• Issue: Missing PyErr_NoMemory in _zoneinfo load_data and ts_to_local #146092

[StanFromIreland]

Please also fix:

https://github.com/python/cpython/blob/main/Modules/_zoneinfo.c#L1872-L1875

[StanFromIreland]

parse_tz_str will then also raise a PyExc_ValueError, this will be confusing for users.

[vstinner]

Oh, I didn't want to raise MemoryError in parse_transition_rule(). I revert this change.

[vstinner]

Please also fix: https://github.com/python/cpython/blob/main/Modules/_zoneinfo.c#L1872-L1875

parse_transition_rule() is only used in parse_tz_str() and parse_tz_str() raises ValueError on parse_transition_rule() failure. Other parse_transition_rule() error paths don't set an exception. So I didn't add PyErr_NoMemory() in parse_transition_rule().

[StanFromIreland]

So I didn't add PyErr_NoMemory() in parse_transition_rule().

Can you please clarify why? The ValueError message may be misleading: "Malformed transition rule in TZ string"
I would update the check to only raise the ValueError if no other exception is already set.