Add timeout in seconds to exc message

distributed/utils_test.py

@@ -981,7 +981,7 @@ async def coro():
                             while not task.cancelled():
                                 await asyncio.sleep(0.01)
                             raise TimeoutError(
-                                f"Test timeout.\n{buffer.getvalue()}"
+                                f"Test timeout after {timeout}s.\n{buffer.getvalue()}"
                             ) from None
                         finally:
                             if client and c.status not in ("closing", "closed"):