Why up2date/rhn_register fails with "ImportError: cannot import name rpclib" error ?

Issue

• Up2date and rhn_register fails with following error

  # up2date -l 
  Traceback (most recent call last): 
    File "/usr/sbin/up2date", line 28, in ? 
      from up2date_client import repoDirector 
    File "/usr/share/rhn/up2date_client/repoDirector.py", line 5, in ? 
      import rhnChannel 
    File "/usr/share/rhn/up2date_client/rhnChannel.py", line 10, in ? 
      import up2dateAuth 
    File "/usr/share/rhn/up2date_client/up2dateAuth.py", line 5, in ? 
      import rpcServer 
    File "/usr/share/rhn/up2date_client/rpcServer.py", line 23, in ? 
      from rhn import rpclib 
  ImportError: cannot import name rpclib