Basic pack job step running in separate MPI_COMM_WORLDs

$ srun --pack-group=1,2 -l tmp
0: JOBID:43740 HOST:nid00002
0: JOBID:43741 HOST:nid00003
1: JOBID:43741 HOST:nid00003
1: JOBID:43740 HOST:nid00002
2: JOBID:43740 HOST:nid00002
2: JOBID:43741 HOST:nid00003
3: JOBID:43741 HOST:nid00003
srun: error: Task 0 reported exit for a second time.
srun: error: Task 1 reported exit for a second time.
srun: error: Task 2 reported exit for a second time.