def setUp(self):
        super(SimpleInstanceTest, self).setUp()
        db_info = DBInstance(
            InstanceTasks.BUILDING, name="TestInstance")
        self.instance = SimpleInstance(
            None, db_info, InstanceServiceStatus(
                ServiceStatuses.BUILDING), ds_version=Mock(), ds=Mock())
        db_info.addresses = {"private": [{"addr": "123.123.123.123"}],
                             "internal": [{"addr": "10.123.123.123"}],
                             "public": [{"addr": "15.123.123.123"}]}
        self.orig_conf = CONF.network_label_regex
        self.orig_ip_regex = CONF.ip_regex
        self.orig_black_list_regex = CONF.black_list_regex
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)