Bad error message when antechamber executable not found

[mattwthompson]

I don't have the time to fix this now, but it stands out and should be noted. This error message is misleading/wrong:

openff-toolkit/openff/toolkit/utils/ambertools_wrapper.py

Lines 194 to 199 in 1feb83d

	ANTECHAMBER_PATH = which("antechamber")
	if ANTECHAMBER_PATH is None:
	raise AntechamberNotFoundError(
	"Antechamber not found, cannot run charge_mol()"
	)

as there is no charge_mol in the toolkit. A minimal fix would be updating the error message, a nicer one would mock the executable as missing.

[j-wags]

Thanks, happy to take a PR for this. I think just updating the message is sufficient.