crunch-job should check errors from open() calls
Undetected open() errors could be causing the "missing stderr" bug mentioned in #12550.
Specifically, each task child process relies on this to capture stderr from srun:
#3 Updated by Tom Clegg about 3 years ago
If this makes any difference at all, it'll make the affected jobs fail (not as good as tempfail, but better than causing downstream failures that are really hard to recover from because job-reuse). By doing so it will also tell us what the open() errors are. Then we can figure out how to either prevent the errors from happening at all and/or recover from them more gracefully.