filter set_event_loop deprecation warning

tornado/testing.py

@@ -159,6 +159,15 @@ def setUp(self) -> None:
         if type(self).get_new_ioloop is not AsyncTestCase.get_new_ioloop:
             warnings.warn("get_new_ioloop is deprecated", DeprecationWarning)
         self.io_loop = self.get_new_ioloop()
+        if ((3, 14, 0) <= py_ver):
+            # Early releases in the Python 3.10 and 3.1 series had deprecation
+            # warnings that were later reverted; we must suppress them here.
+            setup_with_context_manager(self, warnings.catch_warnings())
+            warnings.filterwarnings(
+                "ignore",
+                message="'asyncio.set_event_loop' is deprecated",
+                category=DeprecationWarning,
+            )
         asyncio.set_event_loop(self.io_loop.asyncio_loop)  # type: ignore[attr-defined]
 
     def tearDown(self) -> None: