If creating a symlink from link to a target, determine if target
	is a directory (relative to dirname(link)).

def _is_target_a_directory(link, rel_target):
	"""
	If creating a symlink from link to a target, determine if target
	is a directory (relative to dirname(link)).
	"""
	target = os.path.join(os.path.dirname(link), rel_target)
	return os.path.isdir(target)