[issue35790] Correct the description of sys.exc_info() and add a code example

[Julien Palard]

Change by Julien Palard <julien+python at palard.fr>:


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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35790>
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