pktools/lib/utils.py: Improved error messages for rom factory
pktools/lib/utils.py: Improved error messages for rom factory

Changed the rom_factory method to better handle exceptions and
exception causes.

Signed-off-by: MegaMetapod <48ee6722255b619da9249aa56ff43c3552d60ba3@users.noreply.github.com>

MegaMetapod/pypktools