Better catching of HTTP 401 errors

[caufieldjh]

Right now, if an API isn't accessible due to missing or incorrect credentials, litellm encounters the resulting 401 error. It looks like this:

Error code: 401 - {'error': {'message': 'Authentication Error, Invalid proxy server token passed', 'type': 'auth_error', 'param': 'None', 'code': '401'}}

That's fine, and that error should be raised, but when processing multiple documents with an extraction the process will just move on to the next document and yield an empty result for the current one. That isn't ideal in the case of missing auth as it won't resolve itself without user input.

Authentication errors should be a hard stop.

[caufieldjh]

Might want to add 429 errors, too.

[caufieldjh]

Related to #368