SSL Certificate Verification Error

You may run into this error in your custom app when attempting to connect to an endpoint outside of Frappe Cloud. This tends to happen due to 2 reasons mainly:

1. SSL is not configured correctly on the server you are trying to connect to. It may be not serving the full chain of certificates and hence python's SSL module cannot validate the TLS connection. Browsers can however connect to such servers as they implement AIA. You can verify this by using online tools like https://www.ssllabs.com/. In this case, the server should be correctly configured to serve the full chain of certificates.
2. Python can't use OS certificate store. To resolve this, you can install pip-system-certs package in your custom app as suggested in this stackoverflow thread.