Here we go:

```
$ python3.7 demo.py 
utf-8
UTF-8
Traceback (most recent call last):
  File "demo.py", line 21, in <module>
    asyncio.run(main())
  File "/usr/lib/python3.7/asyncio/runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.7/asyncio/base_events.py", line 568, in run_until_complete
    return future.result()
  File "demo.py", line 14, in main
    sys.stdout.write(out.decode('utf-8'))
UnicodeEncodeError: 'ascii' codec can't encode character '\xe9' in position 1: ordinal not in range(128)
```