Client and server cannot communicate if one is Python 2 and the other is Python 3

[nickwilliams-eventbrite]

If the SOA client is on Python 2 while the server is on Python 3, or vice versa, they are not able to communicate due to missing key errors, because the top-level request message keys on the Python 2 side are serialized as non-unicode, while the top-level response message keys on the Python 3 side are expected to be unicode and are actually bytes.