The only external uses I know of currently are the imports of percolator/colorizer and textview in turtledemo.  There is currently a coloring glitch in 3.5 which continues in 3.6 after the renames.  See #27117.  I won't be surprised if making the colorizer easier to test (by adding an option to explicity pass a color scheme, for instance) makes it easier to use.

I will keep other uses in mind if informed about them.

My careful use tests also pinned down an existing and bizarre glitch in tkinter.simpledialog, reported in #27115.