vicc: temporarily drop python3 compatibility for relay

fixes https://github.com/frankmorgner/vsmartcard/issues/129

virtualsmartcard/src/vpicc/virtualsmartcard/cards/Relay.py

@@ -83,7 +83,7 @@ class RelayOS(SmartcardOS):
                 logging.error("Error getting ATR: %s", e.message)
                 sys.exit()
 
-        return b"".join([bytes(b) for b in atr])
+        return "".join([chr(b) for b in atr])
 
     def powerUp(self):
         # When powerUp is called multiple times the session is valid (and the