Get CASA 4.2.0 trunk building on a RHEL 6.x system as quickly as possible. Issues are most likely to caused by missing or obsolete rpms.
Start with rpms from Redhat repositories. Fill in missing rpms as necessary from Scientific Linux, CentoOS, and Fedora (in that order) repositories as necessary. As a last resort, build additional rpms.
Collected required rpms into a new yum repository on casa.nrao.edu.
Create a meta rpm to support setting up a CASA RHEL 6.x build computer with one yum command to install one meta rpm.