System registration fails with "exceptions.AttributeError" error

Issue

• System registration fails with "exceptions.AttributeError" error,

# rhnreg_ks --username=username --password=password 
An error has occurred: 
exceptions.AttributeError 
See /var/log/up2date for more information 

up2date logs shows,

  File "/usr/sbin/rhnreg_ks", line 284, in main
    rhnreg.getCaps()
   File "/usr/share/rhn/up2date_client/rhnreg.py", line 345, in getCaps
    s = rpcServer.getServer()
   File "/usr/share/rhn/up2date_client/rpcServer.py", line 191, in getServer
    password=proxyPassword)
   File "/usr/lib/python2.3/site-packages/rhn/rpclib.py", line 153, in __init__
    type = (string.lower(type)).strip()
   File "/usr/lib/python2.3/string.py", line 55, in lower
    return s.lower()