I've encountered this while trying to write a program that allowed the user to edit button labels, by creating an Entry widget on top of the  Button, and then hiding the Button. 

Sample code:

http://pastebin.com/WvBbLsNj

According to feedback from stackoverflow, it works as intended on MacOS and Debian. It does not work in Windows (I've tried Windows 7, 8, and Server 2012 R2, with Python versions 2.7.5 to 2.7.9.)

The problem is that the button does not want to stay hidden. E.g. I create an Entry widget and it initially appears on top of the Button. Then, if I click inside the entry box, it briefly disappears (for a second or two), showing the button again, and then reappears. If I hit 'tab' and move focus out of the Entry, it disappears completely (exposing the button again) and only reappears when I click back into the entry/button area.