[misc] error early for old-style class (#10304)

Signed-off-by: youkaichao <youkaichao@gmail.com>

vllm/model_executor/models/medusa.py

@@ -44,7 +44,7 @@ class Medusa(nn.Module):
        in the draft checkpoint (using key token_map). Also, the draft config
        needs to have truncated_vocab_size (=k) as an attribute."""
 
-    def __init__(self, vllm_config: VllmConfig, prefix: str = "") -> None:
+    def __init__(self, *, vllm_config: VllmConfig, prefix: str = "") -> None:
         config = vllm_config.model_config.hf_config
         super().__init__()
         self.config = config