patch_stdout

Hi, I have problems with an ./asyncio-prompt.py example. Running it under Ubuntu 18.10, Python 3.6.8 source taken from git master branch (today) I encountered :

./asyncio-prompt.py
Traceback (most recent call last):
File "./asyncio-prompt.py", line 64, in
main()
File "./asyncio-prompt.py", line 57, in main
loop.run_until_complete(shell_task)
File "/usr/lib/python3.6/asyncio/base_events.py", line 484, in run_until_complete
return future.result()
File "./asyncio-prompt.py", line 41, in interactive_shell
session = PromptSession('Say something: ')
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/shortcuts/prompt.py", line 433, in init
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/shortcuts/prompt.py", line 671, in _create_application
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/application/application.py", line 260, in init
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/application/current.py", line 61, in output
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/output/defaults.py", line 29, in create_output
AttributeError: 'StdoutProxy' object has no attribute 'isatty'

After adding isatty method (my method returns always True), the error has changed to:

./asyncio-prompt.py
Counter: 0
Traceback (most recent call last):
File "./asyncio-prompt.py", line 64, in
main()
File "./asyncio-prompt.py", line 57, in main
loop.run_until_complete(shell_task)
File "/usr/lib/python3.6/asyncio/base_events.py", line 484, in run_until_complete
return future.result()
File "./asyncio-prompt.py", line 46, in interactive_shell
result = await session.prompt_async ()
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/shortcuts/prompt.py", line 1030, in prompt_async
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/application/application.py", line 738, in run_async
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/application/application.py", line 723, in _run_async2
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/application/application.py", line 664, in _run_async
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/application/application.py", line 878, in _request_absolute_cursor_position
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/renderer.py", line 443, in request_absolute_cursor_position
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/renderer.py", line 435, in do_cpr
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/output/vt100.py", line 663, in ask_for_cpr
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/output/vt100.py", line 634, in flush
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/patch_stdout.py", line 141, in write
File "/usr/local/lib/python3.6/dist-packages/prompt_toolkit-3.0.0-py3.6.egg/prompt_toolkit/patch_stdout.py", line 121, in _write
TypeError: a bytes-like object is required, not 'str'

The only thing I came up to with this then, was to remove "with patch_stdout():" from the example whatsoever.

Best regards.

Reproduce the failure with the asyncio-prompt.py example and the reported Python 3.6 setup. Then inspect prompt_toolkit/patch_stdout.py alongside the traceback paths to understand the isatty and bytes-versus-string errors. Done means the example works without removing patch_stdout().