gh-76637: Note that `undefined` Codec is for testing (#136531)

Closes #76637

diff --git a/Doc/library/codecs.rst b/Doc/library/codecs.rst
index 37bd913b765d2149589b16da99b08005d6d02e92..c5dae7c8e8fd0464299780f95abda0757178ff39 100644 (file)
--- a/Doc/library/codecs.rst
+++ b/Doc/library/codecs.rst
@@ -1395,7 +1395,11 @@ encodings.
 |                    |         | It is used in the Python  |
 |                    |         | pickle protocol.          |
 +--------------------+---------+---------------------------+
-| undefined          |         | Raise an exception for    |
+| undefined          |         | This Codec should only    |
+|                    |         | be used for testing       |
+|                    |         | purposes.                 |
+|                    |         |                           |
+|                    |         | Raise an exception for    |
 |                    |         | all conversions, even     |
 |                    |         | empty strings. The error  |
 |                    |         | handler is ignored.       |