chore: add sitecustomize for plugin loading (#5283)

Signed-off-by: Dariusz Duda <[email protected]>

snap/local/sitecustomize.py

@@ -0,0 +1,26 @@
+"""Dynamically load stage-package from another snap into our sys.path.
+
+https://docs.python.org/3/library/site.html#module-sitecustomize
+"""
+
+import hashlib
+import os
+import sys
+from pathlib import Path
+
+TARGET_HASH = "8641d59472d54186f68939ab09cd4882cfba8f20efe278e6a539973c0b3e512c84d952e80f1d7297f8fd025e6878ea58"
+
+
+def _find_pkg() -> None:
+    for craft_dir in Path("/snap").glob("*craft*/current"):
+        hasher = hashlib.sha3_384()
+        hasher.update(str(craft_dir).encode())
+        pkg_dir_hash = hasher.hexdigest()
+        if pkg_dir_hash != TARGET_HASH:
+            continue
+        pkg_path = craft_dir / "craft-plugins"
+        sys.path.insert(0, os.fspath(pkg_path))
+        return
+
+
+_find_pkg()

snap/snapcraft.yaml

@@ -51,8 +51,12 @@ parts:
     plugin: dump
     organize:
       craft.git: libexec/snapcraft/craft.git
+      # Put sitecustomize in site-packages
+      sitecustomize.py: lib/python3.12/site-packages/sitecustomize.py
+
     stage:
       - "libexec/"
+      - "lib/"
 
   git:
     plugin: nil