Fix many* python scripts in src/

gpu/command_buffer/build_gles2_cmd_buffer.py

-#!/usr/bin/python
-#
+#!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """code generator for GLES2 command buffers."""
 
 import os
 import os.path
 import sys
 import re
@@ skipping 5964 matching lines @@
     gen.WriteCommonUtilsImpl("common/gles2_cmd_utils_implementation_autogen.h")
 
     if options.generate_command_id_tests:
       gen.WriteCommandIdTest("common/gles2_cmd_id_test_autogen.h")
 
     if options.generate_docs:
       gen.WriteDocs("docs/gles2_cmd_format_docs_autogen.h")
 
   if gen.errors > 0:
     print "%d errors" % gen.errors
-    sys.exit(1)
+    return 1
+  return 0
+
 
 if __name__ == '__main__':
-  main(sys.argv[1:])
+  sys.exit(main(sys.argv[1:]))