'Obtain and print expirer statistics
:param hosts: set of hosts to check. in the format of:
set([(\'127.0.0.1\', 6020), (\'127.0.0.2\', 6030)])'

def expirer_check(self, hosts):

    stats = {'object_expiration_pass': [], 'expired_last_pass': []}
    recon = Scout(('expirer/%s' % self.server_type), self.verbose, self.suppress_errors, self.timeout)
    print(('[%s]    Checking    on    expirers' % self._ptime()))
    for (url, response, status, ts_start, ts_end) in self.pool.imap(recon.scout, hosts):
        if (status == 200):
            stats['object_expiration_pass'].append(response.get('object_expiration_pass'))
            stats['expired_last_pass'].append(response.get('expired_last_pass'))
    for k in stats:
        if stats[k]:
            computed = self._gen_stats(stats[k], name=k)
            if (computed['reported'] > 0):
                self._print_stats(computed)
            else:
                print(('[%s]    -    No    hosts    returned    valid    data.' % k))
        else:
            print(('[%s]    -    No    hosts    returned    valid    data.' % k))
    print(('=' * 79))
