depot_tools: Run some tests on Python 3 on the bots.

Bug: 984182
Change-Id: I0b7f1e3e056548a27a416c9b4078e54c9e5d60d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1769400
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@google.com>
Reviewed-by: Andrii Shyshkalov <tandrii@google.com>
diff --git a/tests/gclient_scm_test.py b/tests/gclient_scm_test.py
index 2081446..2a4f3d9 100755
--- a/tests/gclient_scm_test.py
+++ b/tests/gclient_scm_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env vpython3
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.