We're using a Python package that internally uses requests to access an online service. The service is located at https://dsbox02.isi.edu:8888/ . If you follow the link with your browser, you'll see that the page opens up, and that it has a valid certificate.
The following Python code, however, fails:
import requests
requests.get('https://dsbox02.isi.edu:8888')
requests.exceptions.SSLError: HTTPSConnectionPool(host='dsbox02.isi.edu', port=8888): Max retries exceeded with url: / (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1122)')))
This happens on Windows 10 and Python 3.7, Ubuntu 18.04 and Python 3.6 and the python:latest docker image, with Python 3.9. On a Mac with Python 3.8 it does work.
There are some ssl certificates that are not trusted in all web browsers. You may need to install an Intermediate/chain certificate to link it to a trusted root certificate.
The easiest way is to check your website with a ssl checker. Such as: https://www.sslshopper.com/ssl-checker.html#hostname=https://dsbox02.isi.edu:8888/