Why service "vdsm-reg" failed to start after upgrading from Red Hat Gluster Storage 3.0 Update 3 to Red Hat Gluster Storage 3.0 Update 4 ?

Issue

• Why service "vdsm-reg" failed to start after upgrading from Red Hat Gluster Storage 3.0 Update 3 to Red Hat Gluster Storage 3.0 Update 4

• Why service "vdsm-reg" failed in Red Hat Gluster Storage 3.0 Update 4 but not in Red Hat Gluster Storage 3.0 Update 3 ?

~ Snippet from terminal,

# cat /etc/redhat-storage-release 
Red Hat Storage Server 3.0 Update 4

[root@rhs3 ~]# service vdsm-reg start
vdsm-reg: starting
Starting up vdsm-reg daemon: 
Traceback (most recent call last):
  File "/usr/share/vdsm-reg/vdsm-reg-setup", line 31, in <module>
    from ovirtnode import ovirtfunctions
ImportError: No module named ovirtnode
vdsm-reg start                                             [FAILED]
vdsm-reg: ended.