Log messages and --list-images fail to report builds of images without valuesPath

[consideRatio]

As suggested in jupyterhub/zero-to-jupyterhub-k8s#2917 (comment), one could build an image without valuesPath set. It seems we would not report on doing that though, just our updates to the values.yaml file.

Here is some logic that needs to be updated.

chartpress/chartpress.py

Lines 1210 to 1234 in d326521

	# build images
	values_file_modifications = build_images(
	prefix=args.image_prefix or chart.get("imagePrefix", ""),
	images=chart["images"],
	tag=common_image_tag,
	push=args.push,
	force_push=args.force_push,
	force_build=args.force_build,
	skip_build=args.no_build or args.reset,
	base_version=base_version,
	long=args.long,
	builder=args.builder,
	platforms=args.platform,
	)
	# list images
	if args.list_images:
	seen_images = set()
	for key, image_dict in values_file_modifications.items():
	image = "{repository}:{tag}".format(**image_dict)
	if image not in seen_images:
	print(image)
	# record image, in case the same image occurs in multiple places
	seen_images.add(image)
	return