If the cooker encounters an error we're unable to proceed so emit a signal
so that UI's can notify the user and exit.
(Bitbake rev: b6f6edd5090e933ac97a65f93ea9d1b255fca811)
Signed-off-by: Joshua Lock <josh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>