Problem

Fixes #1899.

When the user's temporary drive (or output directory) fills up while a job is running, the underlying OSError carries errno 28 (ENOSPC, "No space left on device"). In JobBase._execute this fell through to the catch-all branch:

else:
    _logger.exception("Exception while running job: %s", str(e), ...)
processStatus = "permanentFail"

…which dumps a stack trace and gives the user no hint that the actual problem is a full disk (the symptom reported on the CWL forum thread linked from the issue: a tool silently produces empty outputs).

Fix

Add a dedicated ENOSPC branch to the existing OSError handler in cwltool/job.py, right next to the ENOENT ("command not found") case that's already special-cased there. It logs a concise, actionable message instead of a traceback:

[job foo] No space left on device. The temporary directory (/tmp/…) and/or
output directory (/…/out) may be full; free up space, or point --tmpdir-prefix
and --outdir at a location with more capacity.

The full traceback is still available with --debug (the branch passes exc_info=runtimeContext.debug, matching the sibling cases). I also changed the existing magic-number e.errno == 2 to the named errno.ENOSPC's counterpart errno.ENOENT for readability, now that errno is imported.

Tests

tests/test_examples.py::test_disk_full_error_message injects an OSError(errno.ENOSPC, …) at the job's output-handling stage (monkeypatching cwltool.job.bytes2str_in_dicts) during a normal echo run, and asserts:

• the message contains "No space left on device" and the --tmpdir-prefix guidance,
• no raw Traceback (most recent call last) is printed,
• exit code is 1 (permanentFail).

I verified this test fails against the unpatched code (it hits the old generic-exception/traceback path), proving it guards the behavior. black, flake8, and isort are clean on the changed files.

This addresses the "provide a better error message" ask in #1899. Actually probing free space ahead of time is a larger, platform-specific change and isn't attempted here.

This change was produced with the assistance of Claude Code (model: Claude Opus). The diff, root-cause analysis, and test were reviewed by a human before submission.