While trying to connect RHEV with RHEV API using the Python SDK, why it is throwing an error?

Issue

from ovirtsdk.api import API
from ovirtsdk.xml import params

try:
    api = API(url="https://rhevm.example.com", 
              username='admin', 
              password="secret_password_here",
              ca_file="rhevm.cer")

• After running above code, it outputs:

Unexpected error: 
status: 401
reason: Unauthorized
detail: HTTP Status 401

• From engine.log:

### Your title here...2013-05-03 08:01:03,840 INFO  [org.ovirt.engine.api.restapi.security.auth.LoginValidator] (ajp-/127.0.0.1:8702-1) Login failure, user: admin domain: null reason: Missing domain component in User Principal Name (UPN)