Salt detects this well:
root@master:~# salt minion cmd.run 'true 1'
minion:
root@master:~# echo $?
0
root@master:~# salt minion cmd.run 'false 1'
minion:
ERROR: Minions returned with non-zero exit code
root@master:~# echo $?
11
root@master:~#
The plugin doesn't detect the error and continues the job.
It would rock if plugin detects this situation and fails the job (or not ? config parameter ?)