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

Author: alclarks

Lib/test/test_argparse.py

@@ -105,7 +105,8 @@ def stderr_to_parser_error(parse_args, *args, **kwargs):
             code = sys.exc_info()[1].code
             stdout = sys.stdout.getvalue()
             stderr = sys.stderr.getvalue()
-            raise ArgumentParserError("SystemExit", stdout, stderr, code)
+            raise ArgumentParserError(
+                "SystemExit", stdout, stderr, code) from None
     finally:
         sys.stdout = old_stdout
         sys.stderr = old_stderr

Misc/ACKS

@@ -312,6 +312,7 @@ Gilles Civario
 Chris Clark
 Diana Clarke
 Laurie Clark-Michalek
+Alexander Clarkson
 Mike Clarkson
 Andrew Clegg
 Brad Clements