Cannot enable snap_scheduler for RHGS: "Another scheduler is active" error

Issue

I'm trying to enable snap_scheduler via the command line, but I get an error stating that another scheduler is active.

For example:

[root@rhgs-phx ~]# snap_scheduler.py init
snap_scheduler: Successfully initialised snapshot scheduler for this node

[root@rhgs-phx ~]# snap_scheduler.py enable
snap_scheduler: Failed to enable snapshot scheduling. Error: Another scheduler is active.