fix(oci): keep installing when an image mountpoint is not a plain directory

- Log and continue when the helper refuses a mountpoint, as the seed capture does
- Nothing is moved in that case, so the image installs as before

oci/remote/install_generic_stack.py

@@ -407,7 +407,11 @@ def attach_mounts(service, temporary):
                 owner = (100000,100000,0o755)
             if mount['type'] == 'managed-volume':
                 from oci_image_mountpoints import normalize
-                normalize(root, [mount['container_path']])
+                try:
+                    normalize(root, [mount['container_path']])
+                except (OSError, ValueError) as error:
+                    # Nothing was moved; the image keeps its files as before.
+                    print(f'Image defaults left in place for {mount["container_path"]}: {error}', file=sys.stderr)
         finally:
             run('pct','unmount',vmid)
         if mount['type']=='managed-volume':

oci/remote/install_oci.sh

@@ -524,7 +524,10 @@ capture_volume_seeds() {
   if (( failed == 0 )); then
     # Data seeds were captured first; prepare the raw image even when the
     # transaction will reuse a persistent disk and therefore skipped seeding.
-    oci_quiet python3 "$SCRIPT_DIR/oci_image_mountpoints.py" "$rootfs" "$DEPLOYMENT_FILE" || failed=1
+    # The helper changes nothing when it refuses a path (a link, another
+    # filesystem); the image then installs as it did before.
+    oci_quiet python3 "$SCRIPT_DIR/oci_image_mountpoints.py" "$rootfs" "$DEPLOYMENT_FILE" \
+      || oci_log "Image defaults left in place: a volume mountpoint of the image is not a plain directory"
   fi
   if (( mounted == 1 )); then
     oci_quiet pct unmount "$VMID" || failed=1

oci/tests/test_image_mountpoints.py

@@ -119,5 +119,15 @@ class ImageMountpointTests(unittest.TestCase):
         self.assertEqual(self.normalize(), [])
 
 
+    def test_installers_keep_installing_when_a_mountpoint_is_refused(self):
+        # A refused path changes nothing, so the image installs as it did before.
+        remote = MODULE.parent
+        script = (remote / 'install_oci.sh').read_text()
+        call = script[script.index('oci_image_mountpoints.py'):]
+        self.assertTrue(call.split('\n', 2)[1].strip().startswith('|| oci_log'))
+        stack = (remote / 'install_generic_stack.py').read_text()
+        block = stack[stack.index('normalize(root, [mount'):][:400]
+        self.assertIn('except (OSError, ValueError)', block)
+
 if __name__ == '__main__':
     unittest.main()