def __create_action(self, main_root):
		action_dir = os.path.join(main_root, 'action')
		safe_mkdir(action_dir)

		actions = set()
		for unit, param in self.__task.data['workflow'].items():
			actions.add(param['type'])
		self.__action_mgr.create_actions(actions, action_dir)
def union(matches, root, cwd):
    """Union a list of matchers.

    If the list is empty, return nevermatcher.
    If the list only contains one non-None value, return that matcher.
    Otherwise return a union matcher.
    """
    matches = list(filter(None, matches))
    if len(matches) == 0:
        return nevermatcher(root, cwd)
    elif len(matches) == 1:
        return matches[0]
    else:
        return unionmatcher(matches)