Follow the Scientific Python Ecosystem Coordination organization's suggestion for Python version and library version support lifetimes.

[marcpaterno]

I suggest we strongly encourage DUNE to officially adopt a Python version (and Python library version) dependency policy following the lead of Scientific Python Ecosystem Coordination (SPEC) policy 000 (https://scientific-python.org/specs/spec-0000). The reasons for doing so are spelled out in the SPEC 0 description, and elsewhere in the SPEC documentation.

Following those guidelines, we would drop support for Python 3.12 (and earlier) by our first release following October 2026. At the time we drop support for Python 3.12, we should review our Python code and C++ Python-support code and remove any complications that exist only to support Python 3.12 and older.