depot_tools: Run Python scripts using vpython (Part 1)

Tbr: iannucci@chromium.org
Bug: 984182
Change-Id: If36722e190d305f89d63dce91d0a600ddc34ebe3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1748589
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
diff --git a/git_rebase_update.py b/git_rebase_update.py
index fa5b5c4..27f76bb 100755
--- a/git_rebase_update.py
+++ b/git_rebase_update.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env vpython
 # Copyright 2014 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.