XML serialization for certain types is broken on Python 3

[stunes]

XML serialization does not work for certain types on Python 3. This is best illustrated by example:

On Python 2.7:

>>> val = pyVmomi.vim.vm.device.VirtualDeviceSpec.FileOperation()
>>> pyVmomi.SoapAdapter.Serialize(val)
'<object xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="https://www.w3.org/2001/XMLSchema" xmlns="urn:vim25" xsi:type="VirtualDeviceConfigSpecFileOperation"></object>'
>>> from six import text_type
>>> isinstance(val, text_type)
False
>>> val.replace
'replace'

On Python 3.4:

>>> val = pyVmomi.vim.vm.device.VirtualDeviceSpec.FileOperation()
>>> pyVmomi.SoapAdapter.Serialize(val)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mstunes/projects/uwsimscripts2/lib/python3.4/site-packages/pyVmomi/SoapAdapter.py", line 154, in Serialize
    SoapSerializer(writer, version, nsMap, encoding).Serialize(val, info)
  File "/home/mstunes/projects/uwsimscripts2/lib/python3.4/site-packages/pyVmomi/SoapAdapter.py", line 227, in Serialize
    self._Serialize(val, info, self.defaultNS)
  File "/home/mstunes/projects/uwsimscripts2/lib/python3.4/site-packages/pyVmomi/SoapAdapter.py", line 405, in _Serialize
    result = XmlEscape(val)
  File "/home/mstunes/projects/uwsimscripts2/lib/python3.4/site-packages/pyVmomi/SoapAdapter.py", line 109, in XmlEscape
    escaped = xmlStr.replace("&", "&amp;").replace(">", "&gt;").replace("<", "&lt;")
TypeError: 'vim.vm.device.VirtualDeviceSpec.FileOperation' object is not callable
>>> 
>>> from six import text_type
>>> isinstance(val, text_type)
True
>>> val.replace
'replace'

At SoapAdapter.py:395 (in SoapSerializer._Serialize), the object is checked for isinstance(val, text_type). The result of that comparison is different across versions: on Python 2.7, text_type is 'unicode'; on Python 3.4, text_type is 'str'. As a result, on Python 2.7, val is explicitly converted to a str, whereas no such conversion happens in 3.4. Also, this object has a 'replace' attribute, which is a real function on str objects, but on a FileOperation object, the 'replace' attribute is not a function. Thus, _Serialize fails at runtime when calling replace() on Python 3.4.