[internal #1848537] Upgrade scripts to use Python3

shebang in DsRestAPI.py changed to call python3

Change-Id: I38b2b916d4c70540faaecd821b5d8d6d1006a112 Signed-off-by: József Gyürüsi jozsef.gyurusi@ericsson.com

demo/WebGUI/python_test.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 #///////////////////////////////////////////////////////////////////////////////
 #// Copyright (c) 2000-2019 Ericsson Telecom AB                               //
 #//                                                                           //