Tweak actor validation

little_boxes/activitypub.py

@@ -419,7 +419,7 @@ class BaseActivity(object, metaclass=_ActivityMeta):
         obj_id = self._actor_id(obj)
         try:
             actor = BACKEND.fetch_iri(obj_id)
-        except (ActivityGoneError, ActivityNotFoundError):
+        except (ActivityGoneError, ActivityNotFoundError, ActivityUnavailableError):
             raise
         except Exception:
             raise BadActivityError(f"failed to validate actor {obj!r}")