Compatibility with Python 3.15

root-python-3.15.patch

@@ -0,0 +1,38 @@
+From 4171724228a849959542fcb0b0c1ec10d8e94999 Mon Sep 17 00:00:00 2001
+From: Jonas Rembser <jonas.rembser@cern.ch>
+Date: Fri, 3 Apr 2026 22:56:04 +0200
+Subject: [PATCH] [Python] Set `__spec__` attribute and not `__cached__` for
+ ROOT facade
+
+The Python documentation [1] says:
+
+> It is strongly recommended that you use module.__spec__.cached instead
+  of module.__cached__.
+
+So this commit suggests to transfer the full `__spec__` attribute from
+the ROOT module to the facade, instead of `__cached__`.
+
+This also avoids errors when importing ROOT with Python 3.15, where
+`__cached__` will cease to be set or taken into consideration by the
+import system or standard library.
+
+Closes #21787.
+
+[1] https://docs.python.org/3/reference/datamodel.html#module.__cached__
+---
+ bindings/pyroot/pythonizations/python/ROOT/_facade.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/bindings/pyroot/pythonizations/python/ROOT/_facade.py b/bindings/pyroot/pythonizations/python/ROOT/_facade.py
+index c22ae40da4c2d..da8b6681ec2f2 100644
+--- a/bindings/pyroot/pythonizations/python/ROOT/_facade.py
++++ b/bindings/pyroot/pythonizations/python/ROOT/_facade.py
+@@ -142,7 +142,7 @@ def __init__(self, module, is_ipython):
+         self.__all__ = module.__all__
+         self.__name__ = module.__name__
+         self.__file__ = module.__file__
+-        self.__cached__ = module.__cached__
++        self.__spec__ = module.__spec__
+         self.__path__ = module.__path__
+         self.__doc__ = module.__doc__
+         self.__package__ = module.__package__