How to use the mackup.constants.MACKUP_CONFIG_FILE function in mackup

def _setup_parser(self, filename=None):
        """
        Configure the ConfigParser instance the way we want it.

        Args:
            filename (str) or None

        Returns:
            SafeConfigParser
        """
        assert isinstance(filename, str) or filename is None

        # If we are not overriding the config filename
        if not filename:
            filename = MACKUP_CONFIG_FILE

        parser = configparser.SafeConfigParser(allow_no_value=True)
        parser.read(os.path.join(os.path.join(os.environ["HOME"], filename)))

        return parser

# Is an old setion is in the config file ?
        old_sections = ["Allowed Applications", "Ignored Applications"]
        for old_section in old_sections:
            if self._parser.has_section(old_section):
                error(
                    "Old config file detected. Aborting.\n"
                    "\n"
                    "An old section (e.g. [Allowed Applications]"
                    " or [Ignored Applications] has been detected"
                    " in your {} file.\n"
                    "I'd rather do nothing than do something you"
                    " do not want me to do.\n"
                    "\n"
                    "Please read the up to date documentation on"
                    "  and migrate"
                    " your configuration file.".format(MACKUP_CONFIG_FILE)
                )