add exception

oxi/manager.py

@@ -54,6 +54,9 @@ class Node:
         if not url.endswith('.json'):
             url += '.json'
         response = self._session.get(url)
+        if response.status_code == 500:
+            log.warning("Oxidized response: %r , %r not found", response.status_code, url)
+            raise ValueError(f'page {url} not found')
         return NodeView(
             session=self._session,
             base_url=self._base_url,