Collect possible issues might come with Python 3.12

[DanielYang59]

Collect some Python 3.12 related issues

Might be good to collect some Python 3.12 related issues.

1. For UserDict, d.get(key) and d[key] return different values, as .get method don't call __getitem__

As previously noticed in #3757 (comment).

2. Vasprun: Two unit tests might fail for the following additional warning:

Testing an element's truth value will raise an exception in future versions. Use specific 'len(elem)' or 'elem is not None' test instead.

pymatgen/tests/io/vasp/test_outputs.py

Lines 302 to 308 in 666e1d7

	def test_unconverged(self):
	filepath = f"{VASP_OUT_DIR}/vasprun.unconverged.xml.gz"
	with pytest.warns(
	UnconvergedVASPWarning, match="vasprun.unconverged.xml.gz is an unconverged VASP run"
	) as warns:
	vasprun_unconverged = Vasprun(filepath, parse_potcar_file=False)
	assert len(warns) == 1

and

pymatgen/tests/io/vasp/test_outputs.py

Lines 647 to 652 in 666e1d7

	def test_potcar_not_found(self):
	filepath = f"{VASP_OUT_DIR}/vasprun.xml.gz"
	# Ensure no potcar is found and nothing is updated
	with pytest.warns(UserWarning, match="No POTCAR file with matching TITEL fields was found in") as warns:
	vasp_run = Vasprun(filepath, parse_potcar_file=".")
	assert len(warns) == 2