[Frontend] Improve error message (#31987)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/entrypoints/test_utils.py

@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+from vllm.entrypoints.utils import sanitize_message
+
+
+def test_sanitize_message():
+    assert (
+        sanitize_message("<_io.BytesIO object at 0x7a95e299e750>")
+        == "<_io.BytesIO object>"
+    )