pytest.raises() as exc_info has no .exception

[janosh]

We're misusing pytest.raises() in at least 4 places in 2 files. 2 Examples below where it should be

- str(context.exception)
+ str(context.value)

pymatgen/pymatgen/io/vasp/tests/test_sets.py

Lines 505 to 516 in ed66c97

	assert "Magmom type conflict" in str(context.exception)
	# Test the behavior of MPRelaxSet to atomacically fill in the missing magmom
	struct = self.structure.copy()
	get_valid_magmom_struct(structure=struct, inplace=True, spin_mode="s")
	struct.insert(0, "Li", [0, 0, 0])
	vis = MPRelaxSet(struct, user_potcar_settings={"Fe": "Fe"}, validate_magmom=False)
	with pytest.raises(TypeError) as context:
	print(vis.get_vasp_input())
	assert "argument must be a string" in str(context.exception)