'Get Responses for challenges from authenticators.'

def _solve_challenges(self):

    resp = []
    with error_handler.ErrorHandler(self._cleanup_challenges):
        try:
            if self.achalls:
                resp = self.auth.perform(self.achalls)
        except errors.AuthorizationError:
            logger.critical('Failure    in    setting    up    challenges.')
            logger.info('Attempting    to    clean    up    outstanding    challenges...')
            raise
    assert (len(resp) == len(self.achalls))
    return resp
