Change usage of exit() to sys.exit()
Change usage of exit() to sys.exit()

sys.exit() is the correct way to terminate.

It is recommended to not use exit() in programs[1]:
    The site module (which is imported automatically during startup,
    except if the -S command-line option is given) adds several
    constants to the built-in namespace. They are useful for the
    interactive interpreter shell and should not be used in programs.

[1] https://docs.python.org/3/library/constants.html#exit

Change-Id: I4bfeba2f351c51a4da2e283ee44e10b76f863ff6

openstack/gertty,stackforge/gertty