Raise the timeout even higher.

backup/backup

@@ -43,7 +43,7 @@ def backup(docker_client, registry, image, tag, dest):
 
 def backup_registry(registry, dest):
     """Backup the images in the registry to the destination."""
-    docker_client = docker.from_env(timeout=300)
+    docker_client = docker.from_env(timeout=600)
     docker_client.ping()
     for image in get_images(registry):
         (dest / image).mkdir(exist_ok=True)