Malformed Faults fail in non-informative ways

[hartsock]

example: LicenseUsageFault

  <soapenv:Body>
    <soapenv:Fault>
      <faultcode>ServerFaultCode</faultcode>
      <faultstring/>
      <detail>
        <LicenseUsageFaultFault xsi:type="LicenseUsageFault">
           <reason>dataTampered</reason></LicenseUsageFaultFault>
      </detail>
    </soapenv:Fault>

The detail tag's first child represents the data type to unmarshal the Fault message envelope's contents into. If that child tag does not have a matching WSDL definition pyVmomi fails to raise the fault. The exception raised is KeyError and contains no details about the fault. Instead, an end user should see additional information so they can report the bug accurately.

This change lets the library dynamically create the new fault data type at runtime.

closes #72

[michaelrice]

impressive sir. 👍

[hartsock]

So far, general feedback I've gotten is this is not the correct approach. I will attempt a different fix for this that will raise a much more informative traceback with the SOAP message details inside it. The goal would be for the traceback at the top most level to include the SOAP XML that the parser could not handle.

[hartsock]

Part of the re-work of this patch slipped in here: 4ab4560

This means we need better coverage than what we have since it should not have been so easy to slide in code that would break the lib in edge-cases like that.