fix test_worker.py::test_io_loop_alternate_loop and test_scheduler.py…

…::test_io_loop

distributed/tests/test_scheduler.py

@@ -1365,15 +1365,13 @@ async def test_update_graph_culls(s, a, b):
     assert "z" not in s.tasks
 
 
-def test_io_loop(loop):
-    async def main():
-        with pytest.warns(
-            DeprecationWarning, match=r"the loop kwarg to Scheduler is deprecated"
-        ):
-            s = Scheduler(loop=loop, dashboard_address=":0", validate=True)
-        assert s.io_loop is IOLoop.current()
-
-    asyncio.run(main())
+@gen_test()
+async def test_io_loop(loop):
+    with pytest.warns(
+        DeprecationWarning, match=r"the loop kwarg to Scheduler is deprecated"
+    ):
+        s = Scheduler(loop=loop, dashboard_address=":0", validate=True)
+    assert s.io_loop is IOLoop.current()
 
 
 @gen_cluster(client=True)

distributed/tests/test_worker.py

@@ -592,16 +592,13 @@ async def test_io_loop(s):
 
 @gen_cluster(nthreads=[])
 async def test_io_loop_alternate_loop(s, loop):
-    async def main():
-        with pytest.warns(
-            DeprecationWarning,
-            match=r"The `loop` argument to `Worker` is ignored, and will be "
-            r"removed in a future release. The Worker always binds to the current loop",
-        ):
-            async with Worker(s.address, loop=loop) as w:
-                assert w.io_loop is w.loop is IOLoop.current()
-
-    await asyncio.to_thread(asyncio.run, main())
+    with pytest.warns(
+        DeprecationWarning,
+        match=r"The `loop` argument to `Worker` is ignored, and will be "
+        r"removed in a future release. The Worker always binds to the current loop",
+    ):
+        async with Worker(s.address, loop=loop) as w:
+            assert w.io_loop is w.loop is IOLoop.current()
 
 
 @gen_cluster(client=True)