Merge fix for issue #11501
diff --git a/Lib/test/support.py b/Lib/test/support.py
index 7a43f97..8d8e187 100644
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -1467,3 +1467,36 @@
ok = can_symlink()
msg = "Requires functional symlink implementation"
return test if ok else unittest.skip(msg)(test)
+
+def patch(test_instance, object_to_patch, attr_name, new_value):
+ """Override 'object_to_patch'.'attr_name' with 'new_value'.
+
+ Also, add a cleanup procedure to 'test_instance' to restore
+ 'object_to_patch' value for 'attr_name'.
+ The 'attr_name' should be a valid attribute for 'object_to_patch'.
+
+ """
+ # check that 'attr_name' is a real attribute for 'object_to_patch'
+ # will raise AttributeError if it does not exist
+ getattr(object_to_patch, attr_name)
+
+ # keep a copy of the old value
+ attr_is_local = False
+ try:
+ old_value = object_to_patch.__dict__[attr_name]
+ except (AttributeError, KeyError):
+ old_value = getattr(object_to_patch, attr_name, None)
+ else:
+ attr_is_local = True
+
+ # restore the value when the test is done
+ def cleanup():
+ if attr_is_local:
+ setattr(object_to_patch, attr_name, old_value)
+ else:
+ delattr(object_to_patch, attr_name)
+
+ test_instance.addCleanup(cleanup)
+
+ # actually override the attribute
+ setattr(object_to_patch, attr_name, new_value)