How to diagnose CERTIFICATE_VERIFY_FAILED on Windows for websites working in browsers?

[dieter]

Chi Hsuan Yen <yan12125 at gmail.com> writes:
> ...
> I found that OpenSSL provides an X509 callback hook that allows clients to
> know why the verification process fails.

For a long time, Python 2 (unlike Python 3) did not perform
certificate validation at all. As a consequence, some developpers
provided the functionality in external packages. Maybe, one of those
exposes the callback you have found.
I never used one of those
packages and cannot provide more information that what I said above.

You might also look at "PyOpenSSL" (--> "PyPI"). Apparently, it supports
callbacks written in Python.
Again, I have not myself used this package.