Migrate test-proxy.py to python3

python/test-proxy.py

-#!/usr/bin/env python2
+#!/usr/bin/env python3
 
-import zmq, sys
+import zmq
+import sys
 
 context = zmq.Context()
 
@@ -18,4 +19,3 @@ zmq.device(zmq.QUEUE, frontend, backend)
 frontend.close()
 backend.close()
 context.term()
-