Yesterday this code was working fine both in local and production servers:
import cloudstorage
def filelist(Handler):
gs_bucket_name=\"/bucketname\"
It's a known bug in the dev_appserver, where the SDK does not cope with the credentials already persisted in earlier versions. For me (on Ubuntu 15.10 with SDK 1.9.33) it helped to simply remove a file:
rm ~/.config/gcloud/application_default_credentials.json
as suggested in the bug issue filed by Jari Wiklund.