     PHASE │ run
  DIRECTOR │ Launched worker 0
     START │ ./plan.py
      FAIL │ ./plan.py
────────────────────────────────── Step info ───────────────────────────────────
Command               ./plan.py
Return code           1
──────────────────────────────── Standard error ────────────────────────────────
Traceback (most recent call last):
  File "${CASE}/./plan.py", line ---, in <module>
    step("echo > foo", out=["${ENV_VAR_TEST_STEPUP_NON_EXISTING}.txt"])
  File "${PWD}/stepup/core/api.py", line ---, in step
    out_paths = [translate(subs(out_path)) for out_path in out_paths]
                           ^^^^^^^^^^^^^^
  File "${PWD}/stepup/core/api.py", line ---, in subs
    raise ValueError(f"Undefined shell variable: {name}")
ValueError: Undefined shell variable: ENV_VAR_TEST_STEPUP_NON_EXISTING
────────────────────────────────────────────────────────────────────────────────
   WARNING │ 1 step(s) failed, see error messages above
   WARNING │ Skipping cleanup due to incomplete build.
  WORKFLOW │ Dumped to .stepup/workflow.mpk.xz
     PHASE │ watch
  DIRECTOR │ Stopping workers.
  DIRECTOR │ See you!
