chore: checkpoint before Python removal

vendor/tokio/tests/task_yield_now.rs

@@ -0,0 +1,24 @@
+#![cfg(all(feature = "full", not(target_os = "wasi"), tokio_unstable))]
+
+use tokio::task;
+use tokio_test::task::spawn;
+
+// `yield_now` is tested within the runtime in `rt_common`.
+#[test]
+fn yield_now_outside_of_runtime() {
+    let mut task = spawn(async {
+        task::yield_now().await;
+    });
+
+    assert!(task.poll().is_pending());
+    assert!(task.is_woken());
+    assert!(task.poll().is_ready());
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn yield_now_external_executor_and_block_in_place() {
+    let j = tokio::spawn(async {
+        task::block_in_place(|| futures::executor::block_on(task::yield_now()));
+    });
+    j.await.unwrap();
+}