code: def _warn_on_old_config(self):
          
          # 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"
                        " <https://github.com/lra/mackup> and migrate"
                        " your configuration file."
                        .format(MACKUP_CONFIG_FILE))
docs: Warn the user if an old config format is detected.