use sys.exit() replace exit()
use sys.exit() replace exit()

exit() is used for interactive shell, it relies on the site module.
sys.exit() is considered good to use in programs.

Change-Id: I77169ce6bf6e2c778013b1260f68093e95178b7f

EntropyWorks/bifrost,openstack/bifrost,bcornec/bifrost,openstack/bifrost,EntropyWorks/bifrost,bcornec/bifrost