[issue16845] warnings.simplefilter should validate input

[Roundup Robot]

Change by Roundup Robot <devnull at psf.upfronthosting.co.za>:


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nosy: +python-dev
nosy_count: 5.0 -> 6.0
pull_requests: +30073
pull_request: https://github.com/python/cpython/pull/31983

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue16845>
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