Use a SimpleNamespace for setdefault compatibility.

Author: jaraco

importlib_resources/tests/compat/py39.py

@@ -3,18 +3,18 @@
 """
 
 import os
+import types
+
+from jaraco.collections import Projection
 
 
 try:
     from test.support import import_helper  # type: ignore
 except ImportError:
+    import test.support
 
-    class import_helper:  # type: ignore
-        from test.support import (
-            modules_setup,
-            modules_cleanup,
-            DirsOnSysPath,
-        )
+    names = 'modules_setup', 'modules_cleanup', 'DirsOnSysPath'
+    import_helper = types.SimpleNamespace(**Projection(names, vars(test.support)))
 
 
 try:

setup.cfg

@@ -34,6 +34,7 @@ testing =
 
 	# local
 	zipp >= 3.17
+	jaraco.collections
 
 docs =
 	# upstream