The virt-who throws error "Couldn't find environment 'not-used'" when configured with 'VIRTWHO_ESX_ENV=not-used'

Issue

• As per documentation VIRTWHO_ESX_ENV should have value not-used but virt-who with this parameter does not work,

# virt-who -d  -o  --esx --esx-owner=ownername --esx-env=not-used --esx-server=aa.bb.cc.dd --esx-username=vcenteradmin --esx-password=password
DEBUG: Virt-who is running in esx mode
DEBUG: Sending update in hosts-to-guests mapping: {564d5762-cf5c-0af3-858b-fc0e4ec4b435: [564dfaa4-87f9-9c58-1ba2-c481e9402d86, 564dcd3b-617b-d9ac-5be5-b2192b53f7ce]}
ERROR: Error in communication with subscription manager, trying to recover:
Traceback (most recent call last):
  File "/usr/share/virt-who/virt-who.py", line 196, in _send
    result = self.subscriptionManager.hypervisorCheckIn(self.options.owner, self.options.env, virtualGuests)
  File "/usr/share/virt-who/subscriptionmanager.py", line 92, in hypervisorCheckIn
    return self.connection.hypervisorCheckIn(owner, env, mapping)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 627, in hypervisorCheckIn
    return self.conn.request_post(url, host_guest_mapping)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 440, in request_post
    return self._request("POST", method, params)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 399, in _request
    self.validateResponse(result)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 424, in validateResponse
    raise RestlibException(response['status'], error_msg)
RestlibException: Couldn't find environment 'not-used'
DEBUG: Sending update in hosts-to-guests mapping: {564d5762-cf5c-0af3-858b-fc0e4ec4b435: [564dfaa4-87f9-9c58-1ba2-c481e9402d86, 564dcd3b-617b-d9ac-5be5-b2192b53f7ce]}
ERROR: Unable to recover