Revert "report up the underlining pymongo errors"

This reverts commit 5eb1e610bf330bfe45be96facedf5d8fcd2ec003.
Revert "add yum module downgrade support"

This reverts commit a53503969bd6d2058dfc78aadd668b5aa1d825a0.
Revert "add mongodb replicaset support"

This reverts commit 7159c68ad45e056a57089e83317a2cea1ae66d98.
yum module downgrade support