parser: Fix parser failing to handle errors when setting up work

The parser is not correctly handling some error conditions when dealing with work units. Failure to spawn work, access files, etc should be returned where appropriate, and be able to abort processing if abort_on_error is set.

In addition some errors are leading to a direct exit without checking for abort_on_error.

BugLink: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=921866 BugLink: http://bugs.launchpad.net/bugs/1815294

Signed-off-by: John Johansen john.johansen@canonical.com