set the __package__ attribute for extension modules

Author: timfel

graalpython/lib-graalpython/python_cext.py

@@ -103,7 +103,15 @@ def _PyModule_CreateInitialized_PyModule_New(name):
         if _imp._py_package_context.endswith(name):
             name = _imp._py_package_context
             _imp._py_package_context = None
-    return moduletype(name)
+    new_module = moduletype(name)
+    # TODO: (tfel) I don't think this is the right place to set it, but somehow
+    # at least in the import of sklearn.neighbors.dist_metrics through
+    # sklearn.neighbors.ball_tree the __package__ attribute seems to be already
+    # set in CPython. To not produce a warning, I'm setting it here, although I
+    # could not find what CPython really does
+    if "." in name:
+        new_module.__package__ = name.rpartition('.')[0]
+    return new_module
 
 
 def PyModule_SetDocString(module, string):