# cat /etc/zabbix/zabbix_agentd.d/userparameter_check_reposync.conf
UserParameter=spacewalk.reposync[*],/usr/local/sbin/check_reposync.py $1

# zabbix_agentd -t spacewalk.reposync[centos7-x86_64.log]
spacewalk.reposync[centos7-x86_64.log]        [t|OK: All good for the repository "centos7-x86_64"]

{somehost.acme.org:spacewalk.reposync[centos7-x86_64.log].str("ERROR")}=1