emrg: installer old-python health check before stop_all (rant 2026-08-19T00:44:52)

[argszero]

Summary

Windows upgrade installs could hard-abort when the old runtime python in the previous install directory was corrupted. Per host rant 2026-08-19T00:44:52 (reproduced on v0.2.51 upgrade): ModuleNotFoundError: No module named 'encodings' at startup — the old python-dist was broken by the earlier v0.2.49/v0.2.50 -I incident, so running stop_all.py with it always failed and aborted the install. Deleting the old install\bin (clean-install path) made the same v0.2.51 package install successfully — the package itself is fine, the upgrade path was the fragile point.

Change

In PrepareToInstall (generated .iss via make-installer.sh), before running stop_all with the old runtime python:

1. Health-check the old python first: python.exe -c "import encodings, sys" (redirected to the log via {cmd}, same pattern as stop_all per R125).
2. If the health check fails (non-zero exit, or cannot even be spawned) → skip stop_all and continue the install (clean-install path). A locked file producing a DeleteFile error is recoverable/retryable; a hard abort from a broken python is not.
3. If it passes → run stop_all exactly as before (existing logic preserved).

The health-check failure details go into the log file + the Setup log (Log(...)).

Verification

• bash -n packaging/make-installer.sh ✓
• .iss heredoc rendered exactly as CI does (stub payload) — generated PrepareToInstall inspected ✓
• New text-assertion test test_make_installer_iss_old_python_health_check + existing test_make_installer_iss_has_prepare_to_install / test_build_runtime_copies_stop_all_not_stop_emrg / test_stop_emrg_cmd_deleted pass (pure text assertions, no iscc/cmd/python execution) ✓
• Import + CLI checks pass ✓
• Agent.md test count 958 → 959 (new test function; guarded by test_doc_counts.py)
• Full CI (incl. Windows iscc compile smoke test) will validate the Inno Pascal syntax

[argszero]

✅ LGTM — cycle 786 (Committer). CI test + test-windows (incl. iscc compile smoke test) both PASS on head 781614f. Health-check pattern verified: skip-on-broken-python preserves the clean-install path, healthy-python path unchanged.

[argszero]

✅ LGTM — cycle 787 (Committer). Independent re-verify: head unchanged (781614f), CI test + test-windows PASS. Diff re-inspected — health-check command pattern, skip-on-failure path (Result stays '' → install continues), and preserved stop_all path all correct. 2/3.

[argszero]

✅ LGTM — cycle 788 (Committer). 3rd consecutive approval. Head unchanged (781614f), CI green, MERGEABLE. Merging.