Work towards getting RPC tests working again

So much has changed since I originally got the RPC tests working many years ago,
most notably modern Linux distros don't even have a way to install python2 via
packages, you have to install from source. Continuing with python2 does not seem
like a good idea, so we begin migrating thigns to Python 3.

Currently running ./test.sh will successfully spin up a test chain but then
the test suite crashes when attempting to send an RPC request, which looks
to be caused by the test suite internals still expecting python2.

qa/rpc-tests/test_framework/authproxy.py

@@ -142,6 +142,7 @@ class AuthServiceProxy(object):
                                'method': self.__service_name,
                                'params': args,
                                'id': AuthServiceProxy.__id_count}, default=EncodeDecimal)
+        print("self.__url.path=" + self.__url.path)
         response = self._request('POST', self.__url.path, postdata)
         if response['error'] is not None:
             raise JSONRPCException(response['error'])