Issue #9554: Use modern unittest features in test_argparse.

Initial patch by Denver Coneybeare and Radu Voicilas.
diff --git a/Misc/ACKS b/Misc/ACKS
index e9a473e..204fd88 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1399,6 +1399,7 @@
 Pauli Virtanen
 Frank Visser
 Johannes Vogel
+Radu Voicilas
 Alex Volkov
 Martijn Vries
 Sjoerd de Vries