docs: Hide conftest at any level (#170)

Now that `conftest` to test examples can live at a higher level in the
directory structure it is better to ignore any `conftest` module, even
if there is a slim chance that anyone could have a `conftest` module
that should be part of the public interface (which will conflict with
`pytest` anyway).

Author: llucax

RELEASE_NOTES.md

@@ -11,3 +11,7 @@ If upgrading `pylint` you might get a few new check errors.
 ### Cookiecutter template
 
 There is no need to regenerate any templates with this release.
+
+## Bug Fixes
+
+- `mkdocs`: The `conftest` module is now properly hidden from the documentation again.

src/frequenz/repo/config/mkdocs/api_pages.py

@@ -35,7 +35,7 @@ def _is_internal(path_parts: Tuple[str, ...]) -> bool:
     def with_underscore_not_init(part: str) -> bool:
         return part.startswith("_") and part != "__init__"
 
-    is_conftest = len(path_parts) == 1 and path_parts[0] == "conftest"
+    is_conftest = path_parts[-1] == "conftest" if path_parts else False
 
     return is_conftest or any(p for p in path_parts if with_underscore_not_init(p))