title: Authenticate Google Cloud Storage Python client with gsutil-generated boto file
body: <p>I'm trying to automate report downloading from Google Play (thru Cloud Storage) using GC Python client library. From the docs, I found that <a href="https://support.google.com/googleplay/android-developer/answer/6135870?hl=en" rel="nofollow noreferrer">it's possible to do it using gsutil</a>. I found this question has been answered <a href="https://stackoverflow.com/questions/42555142/downloading-a-file-from-google-cloud-storage-inside-a-folder">here</a>, but I also found that <code>Client</code> infers credentials from environment and I plan to do this on automation platform with (assumed) no gcloud credentials set.</p>
  <p>I've found that you can <a href="https://stackoverflow.com/questions/15509368/is-it-possible-to-automate-gsutil-login">generate gsutil boto file</a> then use it as credential, but how can I load this into the client library?</p>