RPM upgrade tests fail in buildbot

Error: Package: 2:postfix-2.10.1-6.el7.x86_64 (@anaconda)

           Requires: libmysqlclient.so.18(libmysqlclient_18)(64bit)

           Removing: MariaDB-shared-10.2.1-1.el7.centos.x86_64 (@mariadb)

               libmysqlclient.so.18(libmysqlclient_18)(64bit)

           Updated By: MariaDB-shared-10.2.2-1.el7.centos.x86_64 (/MariaDB-10.2.2-centos7-x86_64-shared)

               Not found

           Available: 1:mariadb-libs-5.5.44-2.el7.centos.x86_64 (base)

               libmysqlclient.so.18(libmysqlclient_18)(64bit)

           Available: 1:mariadb-libs-5.5.47-1.el7_2.x86_64 (updates)

               libmysqlclient.so.18(libmysqlclient_18)(64bit)

           Available: 1:mariadb-libs-5.5.50-1.el7_2.x86_64 (updates)

               libmysqlclient.so.18(libmysqlclient_18)(64bit)

Error: Package: 2:postfix-2.10.1-6.el7.x86_64 (@anaconda)

           Requires: libmysqlclient.so.18()(64bit)

           Removing: MariaDB-shared-10.2.1-1.el7.centos.x86_64 (@mariadb)

               libmysqlclient.so.18()(64bit)

           Updated By: MariaDB-shared-10.2.2-1.el7.centos.x86_64 (/MariaDB-10.2.2-centos7-x86_64-shared)

               Not found

           Available: 1:mariadb-libs-5.5.44-2.el7.centos.x86_64 (base)

               libmysqlclient.so.18()(64bit)

           Available: 1:mariadb-libs-5.5.47-1.el7_2.x86_64 (updates)

               libmysqlclient.so.18()(64bit)

           Available: 1:mariadb-libs-5.5.50-1.el7_2.x86_64 (updates)

               libmysqlclient.so.18()(64bit)

 You could try using --skip-broken to work around the problem