tauto: Update presubmit to use python3

BUG=None
TEST=presubmit on repo upload

Change-Id: I466bc896089b714a38a318cc2013013e190e4d3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/tauto/+/4119770
Reviewed-by: Derek Beckett <dbeckett@chromium.org>
Auto-Submit: Jesse McGuire <jessemcguire@google.com>
Tested-by: Jesse McGuire <jessemcguire@google.com>
Reviewed-by: Jesse McGuire <jessemcguire@google.com>
Commit-Queue: Derek Beckett <dbeckett@chromium.org>
Commit-Queue: Jesse McGuire <jessemcguire@google.com>
diff --git a/src/autotest_lib/PRESUBMIT.py b/src/autotest_lib/PRESUBMIT.py
index 0dba8c8..45d60ba 100644
--- a/src/autotest_lib/PRESUBMIT.py
+++ b/src/autotest_lib/PRESUBMIT.py
@@ -1,7 +1,8 @@
-# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Copyright 2020 The ChromiumOS Authors
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+USE_PYTHON3 = True
 
 def CommonChecks(input_api, output_api):
     """Check common to presubmit / preupload."""