Update to CPython 3.15.0a2

[jjhelmus]

Update the cpython-3.15 target from 3.15.0a1 -> 3.15.0a2

[zanieb]

Exception: missing extension modules from YAML: _math_integer

[jjhelmus]

Dropping these links here for my own benefit:

• What's new in Python 3.15
• Python 3.15 changelog

_math_interger is a new stdlib extension module introduced with the addition of math.integer. See PEP 791 and python/cpython#133909