add rhel8 support

advisories/Dockerfile

@@ -2,7 +2,7 @@ FROM gitlab-registry.cern.ch/linuxsupport/cc7-base:latest
 
 COPY linuxsupport7-stable.repo /etc/yum.repos.d/
 
-RUN yum install -y createrepo_c python-createrepo_c --disablerepo=* --enablerepo=linuxsupport7-stable \
+RUN yum install -y createrepo_c python-createrepo_c --disablerepo=extras --enablerepo=linuxsupport7-stable \
   && yum install -y perl perl-Frontier-RPC-Client perl-Crypt-SSLeay perl-DBI \
       perl-DBD-SQLite perl-XML-Writer \
   && yum clean all