fix the error message

Author: whitphx

Lib/importlib/resources/_common.py

@@ -115,8 +115,8 @@ def from_package(package: types.ModuleType):
 
     if package.__spec__ is None:
         raise TypeError(
-            f"Cannot access resources for '{package.__name__}' "
-            "as it does not correspond to an importable module."
+            f"Cannot access resources for '{package.__name__ or package!r}' "
+            "as it does not appear to correspond to an importable module (its __spec__ is None)."
         )
 
     spec = wrap_spec(package.__spec__)

Lib/test/test_importlib/resources/test_resource.py

@@ -241,7 +241,7 @@ def test_main_module_with_none_spec(self):
 
         self.assertIsNone(mainmodule.__spec__)
 
-        with self.assertRaises(TypeError):
+        with self.assertRaises(TypeError, msg="Cannot access resources for '__main__' as it does not appear to correspond to an importable module (its __spec__ is None)."):
             resources.files(mainmodule)