Set path locations from kytosd API.

        It should not be called directly, but from properties that require a
        running kytosd instance.

def __require_kytos_config(self):
        """Set path locations from kytosd API.

        It should not be called directly, but from properties that require a
        running kytosd instance.
        """
        if self.__enabled is None:
            uri = self._kytos_api + 'api/kytos/core/config/'
            try:
                options = json.loads(urllib.request.urlopen(uri).read())
            except urllib.error.URLError:
                print('Kytos is not running.')
                sys.exit()
            self.__enabled = Path(options.get('napps'))
            self.__installed = Path(options.get('installed_napps'))