it took a while to figure this out, but with the postgres repository that i am using for 9.1, the python-psycopg2 rpm that is installed on my system is from the pgdg91 repository. so i would have to conclude that the psycopg2 driver from that repository is for postgresql-9.1 and not the centos 6.x/postgres-8.4. so hopefully that is sound logic now.
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