package_deb: Clean up pointless exception handling

package_deb: Clean up pointless exception handling

The exception handling in this function seemed mildly crazy. Python will
given perfectly good or in several cases better information if we let its
standard traceback/exception handling happen. Remove the pointless code
along with the duplicated key checking which was broken in the inner loop
by usage of the wrong variable.

(From OE-Core rev: f755b07b528e828618141eda402399d791efba4a)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>