Fix panic in who > /dev/full

[AntoxaBarin]

Fixes #10550

Without fix:

$  who > /dev/full panics:

 ./target/release/coreutils who > /dev/full
thread 'main' (142565) panicked at library/std/src/io/stdio.rs:1165:9:
failed printing to stdout: No space left on device (os error 28)
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
Aborted (core dumped)

With fix:

$  who > /dev/full
who: No space left on device

[oech3]

    failures:
        test_who::test_piped_to_dev_full

    test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 5138 filtered out; finished in 0.11s
    
  stderr ───

    thread 'test_who::test_piped_to_dev_full' panicked at tests/by-util/test_who.rs:291:10:
    Command was expected to fail.
    stdout = 
     stderr = 

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/tail/pipe-f is now passing!

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/pipe-f is now passing!

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/numfmt/numfmt. tests/numfmt/numfmt is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tty/tty-eof (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/printf/printf-surprise is now being skipped but was previously passing.
Note: The gnu test tests/unexpand/bounded-memory is now being skipped but was previously passing.
Congrats! The gnu test tests/cp/copy-FMR is now passing!
Congrats! The gnu test tests/pr/bounded-memory is now passing!
Congrats! The gnu test tests/shuf/shuf-reservoir is now passing!
Congrats! The gnu test tests/sort/sort-stale-thread-mem is now passing!
Congrats! The gnu test tests/sort/sort-u-FMR is now passing!

[AntoxaBarin]

@oech3, seems like network error in the only failed job:

Downloading the image (Fedora-Cloud-Base-Generic-43-1.6.x86_64.qcow2)
time="2026-04-05T09:05:50Z" level=fatal msg="failed to download \"[https://download.fedoraproject.org/pub/fedora/linux/releases/43/Cloud/x86_64/images/Fedora-Cloud-Base-Generic-43-1.6.x86_64.qcow2\](https://download.fedoraproject.org/pub/fedora/linux/releases/43/Cloud/x86_64/images/Fedora-Cloud-Base-Generic-43-1.6.x86_64.qcow2/)": read tcp 10.1.0.168:42398->50.117.120.66:443: read: connection reset by peer"

[oech3]

Would you squash to less commits?

[AntoxaBarin]

@oech3, is this enough?

[oech3]

Thankyou

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/tail/pipe-f is now being skipped but was previously passing.
Congrats! The gnu test tests/seq/seq-epipe is now passing!

[sylvestre]

This branch cannot be rebased due to conflicts

sorry