Comment 5 for bug 1210236

I believe I saw the same thing, and can confirm the only error seen (Unable to load quantum from configuration file /etc/quantum/api-paste.ini) and fix (yum install mysql) running RDO grizzly on CentOS 6. This was seen on a freshly-built system dedicated to quantum (no other OpenStack components, using remote database), perhaps explaining why this isn't a common problem.

Making the openstack-quantum-openvswitch package dependent on the MySQL client/libraries would solve this -- but may not be completely correct, because by default ovs_quantum_plugin.ini specifies sqlite://.

And, back to the initial bug description -- logging the fault (missing MySQL library) may be the best answer.