Google Calendar API - no longer authorized for reads?

I don't like adding +1 type responses, but I also suddenly got errors using API keys for the Google Calendar API.

Looking in the Google Console you can see that "API keys" is no longer an enabled credential for the Google Calendar API.

I'm pretty sure it's a mistake as Google should notify everyone before such a huge change. I'm hopeful they find reports of this and it's a mistake that will correct itself soon.

Btw, for anyone else, this is the error returned by Googles API:

{
    "error": {
    "errors": [
    {
    "domain": "global",
    "reason": "authError",
    "message": "Invalid Credentials",
    "locationType": "header",
    "location": "Authorization"
    }
    ],
    "code": 401,
    "message": "Invalid Credentials"
    }
    }

This is now fixed by Google. All API key usage should be working as normal.

Looks like they had some issues on their end: