Fix a test

Due to 3474efca6496e8ff762811b4f35bb4b00b58365b this no longer raises an
exception. We should probably do something here (i.e. report command not found
or whatever), but it definitely shouldn't crash qsh.
Fix test

Looks like this was an accidental change in
9bab48c8debca6ac8371062e206c89e21514b112.
Remove all references to _abort

This is unused (it is not set anywhere any more) so we can delete it.