'Cleanup challenges.
If achall_list is not provided, cleanup all achallenges.'

def _cleanup_challenges(self, achall_list=None):

    logger.info('Cleaning    up    challenges')
    if (achall_list is None):
        achalls = self.achalls
    else:
        achalls = achall_list
    if achalls:
        self.auth.cleanup(achalls)
        for achall in achalls:
            self.achalls.remove(achall)
