After Popen succeeds with os.setsid (detached process group), 5 things
happen with no try/except: Thread construction, reader.start(), lock
acquisition, prune+register, checkpoint write. If any raises, the
Popen object goes unregistered and the detached process group leaks
indefinitely.
Wrap the post-spawn setup in try/except. On failure:
- os.killpg(getpgid(pid), SIGKILL) takes down the entire process
group (not just the shell - important because of detached PG +
-lic shell wrapper that may have spawned children)
- proc.kill() fallback for ProcessLookupError/PermissionError/OSError
- proc.wait(timeout=5) reaps with a bound
- re-raise to preserve original traceback
Nested try/except around cleanup so a secondary failure can't mask the
original.
Closes#2749.
Wesley Simplicio
53ec32819c