def __create_navigator(self, main_root):
		navigator_dir = os.path.join(main_root, 'navigator')
		safe_mkdir(navigator_dir)

		navigators = self.__config_mgr.navigator()
		self.__navigator_mgr.create_navigators(navigators, navigator_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)