Alright, it is compiling under both versions and passing the tests on 2.6. Right now we have some issues with the bytes/unicode changes that need discussion.
Since dbus specifies that signatures, object_paths, service names, etc. are all ascii I have decided to make them all subclass the Bytes type. This make it much faster to extract them as we don't have to encode to bytes first and then extract the char *, but b'a' != 'a' in the test cases. We could have separate test cases for 2.x and 3.x or we could just move to Unicode for everything. I'm not sure what is best.