IssueTracker

Problem you have encountered:
There is no way of checking the occurrence of authentication errors in logs explorer while calling Vision API.

What you expected to happen:
To be able to see the policy denied logs after failed authentication errors such as [1].

Steps to reproduce:
1. Followed this quickguide and try to fail the authentication: https://cloud.google.com/vision/docs/quickstart-cli 
2. Check for the failed authentication attempt in cloud logging(only successful cloud logging attempts are logged in Cloud logging)

Other information (workarounds you have tried, documentation consulted, etc):
Here it says that Vision API does not have Policy denied logs (https://cloud.google.com/logging/docs/audit/services )

[1] 'message:401 Request had invalid authentication.
credentials. Expected OAuth 2 access token,
login cookie or other valid authentication credential.
See
https://developers.google.com/identity/sign-in/web/devconsole-project.
[reason:"ACCESS_TOKEN_EXPIRED"
domain: "googleapis.com"
metadata {
key: "service"
value: "vision.googleapis.com"
}
metadata {
key: "method"
value:
"google.cloud.vision.v1.ImageAnnotator BatchAnnotatelmages"