We shouldn't be generating exception inside a generator. Rearrange the
code to improve the handling of this. Also fix the misconverted code
from when multiconfig was added and pass the exception as "result".
(Bitbake rev: ae89e23696de2f27c00ae00922933395171de5d5)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>