I've just installed py2app 0.26 since I need the new SSL recipe, however, it appears to be displaying only a black Tkinter window upon launch.
Just seeing if anyone else is encountering this issue and if there have been any workarounds since py2app 0.26 has been released.
This is caused by a bug in py2app 0.26 in combination with the "Intel" variant of the Python.org installer for macOS.   The bug is fixed in py2app 0.26.1.
py2app 0.26 Black Tkinter window