How to deal with "Cannot complete login due to an incorrect user name or password" error of virt-who ?

Issue

• Can not use virt-who. After restarting virt-who service , below errors come out :

2016-02-02 09:52:51,375 [ERROR]  @virt-who.py:184 - Unable to recover, retry in 60 seconds.
2016-02-02 09:54:08,501 [ERROR]  @virt-who.py:181 - Unable to create connection:
Traceback (most recent call last):
  File "/usr/share/virt-who/virt-who.py", line 178, in _send
    self.checkConnections()
  File "/usr/share/virt-who/virt-who.py", line 157, in checkConnections
    self.initVirt()
  File "/usr/share/virt-who/virt-who.py", line 107, in initVirt
    self.virt = VSphere(self.logger, self.options.server, self.options.username, self.options.password)
  File "/usr/share/virt-who/vsphere.py", line 129, in __init__
    self.client.service.Login(_this=self.sc.sessionManager, userName=username, password=password)
  File "/usr/lib/python2.6/site-packages/suds/client.py", line 542, in __call__
    return client.invoke(args, kwargs)
  File "/usr/lib/python2.6/site-packages/suds/client.py", line 602, in invoke
    result = self.send(soapenv)
  File "/usr/lib/python2.6/site-packages/suds/client.py", line 657, in send
    result = self.failed(binding, e)
  File "/usr/lib/python2.6/site-packages/suds/client.py", line 712, in failed
    r, p = binding.get_fault(reply)
  File "/usr/lib/python2.6/site-packages/suds/bindings/binding.py", line 265, in get_fault
    raise WebFault(p, faultroot)
WebFault: Server raised fault: 'Cannot complete login due to an incorrect user name or password.'
2016-02-02 09:54:26,745 [ERROR]  @virt-who.py:184 - Unable to recover, retry in 60 seconds.