Include actor URI in another error

Fixes #331

users/models/identity.py

@@ -718,7 +718,8 @@ class Identity(StatorModel):
             return False
         if response.status_code >= 400:
             raise ValueError(
-                f"Client error fetching actor: {response.status_code}", response.content
+                f"Client error fetching actor at {self.actor_uri}: {response.status_code}",
+                response.content,
             )
         document = canonicalise(response.json(), include_security=True)
         if "type" not in document: