On 2016-11-29 15:40, Davor Rotim wrote:
> I started with:
> 
> emacs -Q --eval `(setq python-shell-interpreter "python3")'
> 
> then did `M-x run-python' and I was greeted by the same warning.
> 
> Tried `M-x find-function python-shell-completion-native-try' and the "_" addition is there.
> 
> http://i.imgur.com/rEDklpI.png

Hmm. Can you try the following? M-x run-python, then with the *Python* buffer current do (python-shell-completion-native-try).  Does this return a list of strings?

What about 

  (python-shell-completion-native-get-completions (get-buffer-process (current-buffer)) nil "imp")

Thanks!