[issue33109] argparse: make new 'required' argument to add_subparsers default to False instead of True

[Ned Deily]

Change by Ned Deily <nad at python.org>:


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keywords: +patch
pull_requests: +6587
stage:  -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33109>
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