**/*.py: use /usr/bin/env to find python

tests/abi_corpus/startup_regression_test.py

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import optparse
 import os
 import re
 import sys
 import tempfile
 
@@ skipping 138 matching lines @@
   work_dir = tempfile.mkdtemp(suffix='startup_crxs', prefix='tmp')
   work_dir = os.path.realpath(work_dir)
   try:
     TestApps(options, work_dir)
   finally:
     corpus_utils.RemoveDir(work_dir)
 
 
 if __name__ == '__main__':
   Main()