[issue38341] Add SMTPNotSupportedError in the exports of smtplib

[Roundup Robot]

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


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keywords: +patch
pull_requests: +16116
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/16525

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue38341>
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