SSLHandshakeError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed
Use case
On a local network set up with a firewall that does local packet inspection, you can get the following error message:
SSLHandshakeError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:727)
This error occurs due to firewalls often getting configured with a self-signed certificate that your network administrator created themselves, and that Python does not have access to. Unfortunately, unlike other applications, Python does not always look inside the OS’s keychain for certificates, so you have to provide it yourself.
How to fix
You need to set the SHOTGUN_API_CACERTS environment variable to point to a file on disk that contains the complete list of certificate authorities the Python API and Shotgun Desktop can trust.
You can download such a copy from the latest copy of the certifi package on Github. Once you’ve done this, you need to add the public key of your corporate firewall at the bottom of that file and save it.
Once this is done, simply set SHOTGUN_API_CACERTS environment variable to the path location, e.g. /opt/certs/cacert.pem and launch the Shotgun Desktop.