Add channel-aware release tooling and updater recovery

ptlinux/self_update.py

@@ -2253,6 +2253,7 @@ def _extract_release_archive(archive: Path, destination: Path, version: str) ->
 def _validate_release_directory(release: Path) -> str:
 	if not release.is_dir() or release.is_symlink():
 		raise LauncherUpdateError(f"launcher release directory is invalid: {release}")
+	_remove_generated_bytecode_caches(release)
 	for item in (release, *release.rglob("*")):
 		if item.is_symlink():
 			raise LauncherUpdateError(f"launcher release contains a symbolic link: {item}")
@@ -2302,6 +2303,43 @@ def _validate_release_directory(release: Path) -> str:
 	return version
 
 
+def _remove_generated_bytecode_caches(release: Path) -> None:
+	"""Remove interpreter caches that are never part of a signed release."""
+
+	try:
+		cache_directories = sorted(
+			release.rglob("__pycache__"),
+			key=lambda path: len(path.parts),
+			reverse=True,
+		)
+	except OSError as exc:
+		raise LauncherUpdateError(
+			f"cannot inspect launcher bytecode caches in {release}: {exc}"
+		) from exc
+	for cache in cache_directories:
+		if cache.is_symlink() or not cache.is_dir():
+			raise LauncherUpdateError(f"launcher bytecode cache is unsafe: {cache}")
+		try:
+			entries = tuple(cache.iterdir())
+		except OSError as exc:
+			raise LauncherUpdateError(
+				f"cannot inspect launcher bytecode cache {cache}: {exc}"
+			) from exc
+		for entry in entries:
+			if entry.is_symlink() or not entry.is_file() or entry.suffix not in {".pyc", ".pyo"}:
+				raise LauncherUpdateError(
+					f"launcher bytecode cache contains an unexpected path: {entry}"
+				)
+		try:
+			for entry in entries:
+				entry.unlink()
+			cache.rmdir()
+		except OSError as exc:
+			raise LauncherUpdateError(
+				f"cannot remove launcher bytecode cache {cache}: {exc}"
+			) from exc
+
+
 def _self_check_release(release: Path, expected_version: str) -> None:
 	check = (
 		"import sys; "