The CentOS SoftwareCollections SIG repo signature is invalid:
[root@vm5 ~]# curl -s -O http://mirror.centos.org/centos/7.6.1810/sclo/x86_64/sclo/repodata/repomd.xml.asc
[root@vm5 ~]# curl -s -O http://mirror.centos.org/centos/7.6.1810/sclo/x86_64/sclo/repodata/repomd.xml
[root@vm5 ~]# gpg repomd.xml.asc
gpg: Signature made Sat 19 May 2018 02:44:12 AM CEST using RSA key ID F2EE9D55
gpg: BAD signature from "CentOS SoftwareCollections SIG (https://wiki.centos.org/SpecialInterestGroup/SCLo) <security@centos.org>"