There are several problems with the patch provided in msg156315

This description:

"Added patch so that only the first '--' is removed by an argparse.PARSE or argparse.REMAINDER argument."

should read

"Added patch so that only the first '--' is removed by arguments that are not argparse.PARSER or argparse.REMAINDER ."

The test that adds a third subparser with a nargs='...' argument does not test this change.   It exercises both nargs types that are not affected by the change in argparse.py.  As such older versions of argparse pass this test.

I thinking argparse.py change is correct (delete only the 1st '--'), though I'm not sure it addresses the concern of the original poster.