RuntimeWarning: coroutine 'EventSourceResponse.send' was never awaited

[d21d3q]

Problem occurred yesterday in my project, I spent half day undoing commits to have it back working...
Now I tried to run simple.py demo from this repo and I'm having the same problem.

Steps to reproduce

git clone <aiohttp_sse>
cd aiohttp_sse
virtualenv -p python3.6 venv
source venv/bin/activate
pip install aiohttp aiohttp_sse
python examples/simple/py

and after opening localhost:8080/index browser shows only Response from server:
and console shows this output:

======== Running on http://127.0.0.1:8080 ========  
(Press CTRL+C to quit)                              
foo                                                 
examples/simple.py:12: RuntimeWarning: coroutine 'EventSourceResponse.send' was never awaited
  resp.send('foo {}'.format(i))                     
foo                                                 
foo                                                 
...

wireshark doesn't show any traffic after GET /hello. only some TCP ACK.
is it possible that it crashes somewhere inside aiohttp?

[d21d3q]

And here is origin of problem. aiohttp changed api