Merge remote-tracking branch 'upstream/master'

Author: Orest Bolohan

samples/call_compute_service.py

@@ -1,5 +1,8 @@
 # To be used to test GoogleCredentials.get_application_default()
 # from local machine and GCE.
+# The GCE virtual machine needs to have both service account and
+# Compute API enabled.
+# See:  https://developers.google.com/compute/docs/authentication
 
 from googleapiclient.discovery import build
 from oauth2client.client import GoogleCredentials