VMware ESXi ホストで virt-who が機能しないのはなぜですか?

Issue

• virt-who が ESXi ホストと機能せず、以下のトレースバックが表示されます。

  @virt-who.py:186 - Error in communication with virt backend, trying to recover:
Traceback (most recent call last):
  File "/usr/share/virt-who/virt-who.py", line 180, in _send
    virtualGuests = self.virt.getHostGuestMapping()
  File "/usr/share/virt-who/vsphere.py", line 268, in getHostGuestMapping
    self.scan()
  File "/usr/share/virt-who/vsphere.py", line 216, in scan
    for propSet in obj.propSet:
AttributeError:'unicode' object has no attribute 'propSet'
2013-03-26 10:47:14,098 [ERROR]  @virt-who.py:189 - Unable to recover, retry in 60 seconds.