I'm trying to upgrade my Ovirt from version 4.1 to 4.2, but I'm stuck when issuing the command  engine-setup which returns the following errors :

                Upgrading PostgreSQL
[ ERROR ] Failed to execute stage 'Misc configuration': Command '/opt/rh/rh-postgresql95/root/usr/bin/postgresql-setup' failed to execute
[ INFO  ] Yum Performing yum transaction rollback
[ INFO  ] Rolling back to the previous PostgreSQL instance (postgresql).
[ INFO  ] Stage: Clean up Log file is located at /var/log/ovirt-engine/setup/ovirt-engine-setup-20180426122630-rpkrel.log
[ INFO  ] Generating answer file '/var/lib/ovirt-engine/setup/answers/20180426122823-setup.conf'
[ INFO  ] Stage: Pre-termination
[ INFO  ] Stage: Termination
[ ERROR ] Execution of setup failed