I'm trying to use bigrquery from within a docker container that runs on Kubernetes Engine. credentials_app_default() fails to authenticate and the browser option gets triggered through credentials_user_oauth2(). I don't experience this issue when I run the container on a GCE VM as credentials_gce() takes care of authentication.

The same container runs fine on Kubernetes Engine if I replace bigrquery with Python's bigquery from google.cloud. As you mentioned in #78, it seems gargle's ADC strategy doesn't quite match https://cloud.google.com/docs/authentication/production:

If the environment variable isn't set, ADC uses the default service account that Compute Engine, Kubernetes Engine, Cloud Run, App Engine, and Cloud Functions provide, for applications that run on those services.