Fix data_entry_flow.UnknownStep error message (#138288)

homeassistant/data_entry_flow.py

@@ -561,7 +561,7 @@ class FlowManager(abc.ABC, Generic[_FlowContextT, _FlowResultT, _HandlerT]):
         if not hasattr(flow, method):
             self._async_remove_flow_progress(flow.flow_id)
             raise UnknownStep(
-                f"Handler {self.__class__.__name__} doesn't support step {step_id}"
+                f"Handler {flow.__class__.__name__} doesn't support step {step_id}"
             )
 
     async def _async_setup_preview(

tests/components/config/test_config_entries.py

@@ -2887,9 +2887,7 @@ async def test_does_not_support_reconfigure(
 
     assert resp.status == HTTPStatus.BAD_REQUEST
     response = await resp.json()
-    assert response == {
-        "message": "Handler ConfigEntriesFlowManager doesn't support step reconfigure"
-    }
+    assert response == {"message": "Handler TestFlow doesn't support step reconfigure"}
 
 
 async def test_list_subentries(