[issue43639] Do not raise AttributeError on instance attribute update/deletion if data descriptor with missing __set__/__delete__ method found on its type

[Raymond Hettinger]

Change by Raymond Hettinger <raymond.hettinger at gmail.com>:


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nosy: +rhettinger
versions:  -Python 3.6, Python 3.7, Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue43639>
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