Fix python scripts in src/tools/

tools/net/netlog.py

Index: tools/net/netlog.py
diff --git a/tools/net/netlog.py b/tools/net/netlog.py
index 610052bbbd70045b1fdd1b03f717bb62c9f0ce31..d3831dfb1f26e939632c60af9cb61cab48535b4e 100755
--- a/tools/net/netlog.py
+++ b/tools/net/netlog.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2010 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.
@@ -172,6 +172,4 @@ def main(_):
 
 
 if '__main__' == __name__:
-  ret = main(sys.argv)
-  sys.exit(ret)
-
+  sys.exit(main(sys.argv))