refactor: keep root install as the sole installer source

test/onboarding/verify_prepared_release.py

@@ -3,7 +3,6 @@
 
 import argparse
 import hashlib
-import importlib.util
 import json
 import os
 from pathlib import Path
@@ -13,6 +12,9 @@ import signal
 import subprocess
 import time
 
+from install_support import load_installer
+
+
 WORKSPACE = Path(__file__).resolve().parents[2]
 OS_LIBRARIES = (
     "libc.so.6", "libdl.so.2", "libm.so.6", "libpthread.so.0", "librt.so.1",
@@ -195,10 +197,7 @@ def ordinary_uid_target_reuse(image):
 def install_assets(assets, image, manifest):
     # Only transport is local: signature verification, full tar extraction and
     # the final bootstrap executable are the real first-install implementation.
-    script = WORKSPACE / "skills/scripts/install.py"
-    specification = importlib.util.spec_from_file_location("dever_release_installer", script)
-    installer = importlib.util.module_from_spec(specification)
-    specification.loader.exec_module(installer)
+    installer = load_installer()
     stem = f"dever-{manifest['platform']}"
     base = installer.RELEASES
     routes = {
@@ -239,7 +238,7 @@ def accept(release, assets, image, report, init, extension_helper=None):
             install_assets(assets, image, manifest)
         else:
             execute([
-                "/usr/bin/python3", WORKSPACE / "skills/scripts/install.py",
+                "/bin/bash", WORKSPACE / "install",
                 "--release", release, "--version", manifest["version"],
                 "--system-root", image,
             ])