[DTensor] Added op_call in no-mesh dispatch assert message (pytorch…

…#113903)

This helps debug, e.g. when there is an unsupported op.
Pull Request resolved: pytorch#113903
Approved by: https://github.com/wanchaol
ghstack dependencies: pytorch#113654

torch/distributed/_tensor/dispatch.py

@@ -326,7 +326,7 @@ def unwrap_to_op_info(
                 kwargs_schema[k] = v
                 local_kwargs[k] = v
 
-        assert mesh is not None, "found no DeviceMesh from dtensor args!"
+        assert mesh is not None, f"found no DeviceMesh from dtensor args for {op_call}!"
         op_info = OpInfo(
             mesh,
             OpSchema(