if I put "import tkinter" in my Python (3.6) file the mac app I get with py2app does not work. 
py2app works just fine with other Python files importing other packages (math, time, random etc) only importing tkinter raises this problem
Solved but I'm not sure it should have to work like this. 
I think the problem is that Mac works with Python 2.7 (system Python) which raises an error when it gets "import tkinter". 
So I installed with Homebrew Python 2.7, redesigned my modules written in P 3.6 ("import Tkinter" etc.) py2app-ed it and everything went fine.
py2app does not work with tkinter