This is also a problem in Python 3.6 with MacOS Sierrra. I know your use case is different. But I stumbled upon this thread while investigating this problem. So if anyone is also having this article is worth checking out:
In a nutshell: Python 3.6 does not rely on MacOS’ openSSL anymore. It comes with its own openSSL bundled and doesn’t have access on MacOS’ root certificates.
You have two options:
Run an install command shipped with Python 3.6
cd /Applications/Python\ 3.6/
./Install\ Certificates.command
or
Install the certifi package with
pip install certifi
I chose the first option and it worked.