sys.exit() calls in main() will make the interactive
python interpreter exit. We can call the main() as
below to avoid to exit the interactive interpreter,
and specify the return value of main() in the exit
code at the same time.
sys.exit(main())
also see: I6ead9853fe27e99df3e9121478e906a06839f48c
Change-Id: I3086dc0529c4343f246f543de1b6ee6540438a98