Explicitly run everything with python3

R=aravindvasudev@google.com, gavinmak@google.com

Change-Id: Iaa5e960c6226dea3a0814c7cb778d952eafb1502
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3525960
Reviewed-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/git_hyper_blame.py b/git_hyper_blame.py
index 6a8dae8..1b63a3b 100755
--- a/git_hyper_blame.py
+++ b/git_hyper_blame.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 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.