bpo-9495: avoid confusing chained exception in argparse test (GH-17120)

diff --git a/Misc/ACKS b/Misc/ACKS
index b11ee9c..976c26e 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -312,6 +312,7 @@
 Chris Clark
 Diana Clarke
 Laurie Clark-Michalek
+Alexander Clarkson
 Mike Clarkson
 Andrew Clegg
 Brad Clements