An implementation of the storagedriver.StorageDriver interface which uses Google Cloud for object storage.
bucket: The name of your Google Cloud Storage bucket where you wish to store objects (needs to already be created prior to driver initialization).
keyfile: (optional) A private key file in JSON format, used for Service Account Authentication.
Note Instead of a key file you can use Google Application Default Credentials.
rootdirectory: (optional) The root directory tree in which all registry files will be stored. Defaults to the empty string (bucket root).