It seems impossible to correctly close() an asyncio Process on which terminate has been invoked. Take the following coroutine:

async def test():
    proc = await asyncio.create_subprocess_shell(
        "sleep 1", stdout=asyncio.subprocess.PIPE)
    proc.terminate()
    await proc.wait()

After running it with asyncio.run(), Python prints a warning about "Event loop is closed" exception ignored in BaseSubprocessTransport.__del__. The code does wait for the process to exit, and neither proc nor proc.stdout have a close() method, so the warning seems spurious.

Commenting out proc.terminate() makes the program finish without an exception (but then it waits for a full second, of course).

Runnable example attached.