Exit normally if registry's storage is empty

In earlier versions of docker-registry, repository enumeration didn't
return error for empty registry storage while the blob enumeration
function did. This case needs to be handled.

Signed-off-by: Michal Minář <[email protected]>

Author: Michal Minář

pkg/dockerregistry/server/prune/prune.go

@@ -192,5 +192,9 @@ func Prune(ctx context.Context, storageDriver driver.StorageDriver, registry dis
 
 		return nil
 	})
+	if e, ok := err.(driver.PathNotFoundError); ok {
+		logger.Warnf("No repositories found: %v", e)
+		return stats, nil
+	}
 	return stats, err
 }