bpo-40499: Mention that asyncio.wait() needs a non-empty aws set (GH-19900)
A similar formulation was added in bpo-21596
(db74d982d43d98040e38665d843cbc8de4a082b1) but was lost in bpo-33649
(3faaa8857a42a36383bb18425444e597fc876797).
diff --git a/Doc/library/asyncio-task.rst b/Doc/library/asyncio-task.rst
index d992b00..6627bec 100644
--- a/Doc/library/asyncio-task.rst
+++ b/Doc/library/asyncio-task.rst
@@ -498,6 +498,8 @@
set concurrently and block until the condition specified
by *return_when*.
+ The *aws* set must not be empty.
+
Returns two sets of Tasks/Futures: ``(done, pending)``.
Usage::