librarian: action required to resolve "author field is required" error is not clear

I am running Librarian in `google-cloud-python` with 

```
LIBRARIAN_GITHUB_TOKEN=$(gh auth token) librarian generate -api=google/cloud/hypercomputecluster/v1beta -library=google-cloud-hypercomputecluster -push
```

and it seems to run and generate (though I do get the warnings in #2687) but then it appears to error with the message `level=INFO msg="author field is required"`