doctest._load_testfile uses deprecated Loader.get_data API, it should use importlib.resources

[graingert]

Bug report

Bug description:

cpython/Lib/doctest.py

Lines 246 to 257 in ae7f621

	if (loader := getattr(package, '__loader__', None)) is None:
	try:
	loader = package.__spec__.loader
	except AttributeError:
	pass
	if hasattr(loader, 'get_data'):
	file_contents = loader.get_data(filename)
	file_contents = file_contents.decode(encoding)
	# get_data() opens files as 'rb', so one must do the equivalent
	# conversion as universal newlines would do.
	return _newline_convert(file_contents), filename
	with open(filename, encoding=encoding) as f:

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-128862: use importlib.resources to acquire doctest resources #128865