Domain users of vsphere not able to login_in_guest()

[sathrian]

I'm trying to open a console of a linux machine. I have logged as domain user, we have role which administrator.
but i'm getting the below error.
s = VIServer()
s.connect(HOST, 'test\suresh', 'password')
vm = s.get_vm_by_name('Linux-one')
vm.login_in_guest('root', 'test123')

Traceback (most recent call last):
File "", line 1, in
File "/root/.pyenv/versions/2.7.10/lib/python2.7/site-packages/pysphere/vi_virtual_machine.py", line 1027, in login_in_guest
self.__validate_authentication(auth)
File "/root/.pyenv/versions/2.7.10/lib/python2.7/site-packages/pysphere/vi_virtual_machine.py", line 1706, in __validate_authentication
raise VIApiException(e)
pysphere.resources.vi_exception.VIApiException: [NoPermissionFault]: Permission to perform this operation was denied.