I need to use curtom root certificates on the company intranet and loading them in the Mac OS TrustStore (KeyChain) does solve the problem for all browsers and GUI apps.
Mac brew install python env.
$ python3
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 16:52:21)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import certifi
>>> certifi.where()
'/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/certifi/cacert.pem'
>>>
Or from the command line:
$ python -m certifi
then need link cacert.pem as cert.pem
$ ln -s /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/certifi/cacert.pem cert.pem
$ pwd
/Library/Frameworks/Python.framework/Versions/3.7/etc/openssl
rehash
then work fine.