Use /usr/bin/python2 in shebangs

Per the pep-0394 recommendation, version specific python scripts should
specify the interpreter version.

TEST=Run tests on a system with python3 default
BUG=None

Change-Id: I83e98f3bb0235230293819104570930085788398
Reviewed-on: https://chromium-review.googlesource.com/251132
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Anatol Pomazau <anatol@google.com>
Commit-Queue: Anatol Pomazau <anatol@google.com>
diff --git a/tests/bitmaps/TestBmpBlock.py b/tests/bitmaps/TestBmpBlock.py
index 8f47fe4..2fcfd66 100755
--- a/tests/bitmaps/TestBmpBlock.py
+++ b/tests/bitmaps/TestBmpBlock.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python -tt
+#!/usr/bin/python2 -tt
 #
 # Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be