Today I ran into a problem when using both tkinter and matplotlib.pyplot at the same time. I thought it would be best to let you know, in case it is an issue. 

The problem is/was that the root window did not close itself, when just using `askopenfilename()`. 

A complete description of the problem, including a minimal working example, screenshots and a "solution" can be found on StackOverflow: 
https://stackoverflow.com/q/45960815/7414040 

I think that the function `askopenfilename()` does not ensure that the tkinter root window, that has been opened, is destroyed after the function call ended.