Save a reference for ensure_future and create_task (GH-29163)

Co-authored-by: Joannah Nanjekye <jnanjekye@python.org>
(cherry picked from commit c750adb)

Co-authored-by: Joannah Nanjekye <33177550+nanjekyejoannah@users.noreply.github.com>

Doc/library/asyncio-future.rst

@@ -54,6 +54,9 @@ Future Functions
       See also the :func:`create_task` function which is the
       preferred way for creating new Tasks.
 
+      Save a reference to the result of this function, to avoid
+      a task disappearing mid execution.
+
    .. versionchanged:: 3.5.1
       The function accepts any :term:`awaitable` object.
 

Doc/library/asyncio-task.rst

@@ -274,6 +274,11 @@ Creating Tasks
        task = asyncio.ensure_future(coro())
        ...
 
+   .. important::
+
+      Save a reference to the result of this function, to avoid
+      a task disappearing mid execution.
+
    .. versionadded:: 3.7
 
    .. versionchanged:: 3.8