title: Specifying Google service account in gsutil for GCP operations
body: <p>It seems Google Cloud SDK requires the service account to be activated via <code>gcloud auth ...</code>. Without it, <code>gsutil cp</code> or <code>gsutil rsync</code> would not work. This does not work very well in the continuous integration environments or other cron-based, when one may have multiple jobs running at the same time, thus creating a potential conflict when different scripts try to use different accounts in parallel.</p>
  
  <p>Is it possible to pass the google service account as a parameter to <code>gsutil</code>? Thanks!</p>