Ned, PR-14616 replaces a dead link to the most important online Tkinter reference.  Please consider cherry-picking the 3.7 backport (already merged) into the upcoming 3.7.4.  Many people are lost without the reference, as they find reading the tcl/tk reference much harder. (The question has come up on Stackoverflow also.) 

I checked that the new link in the rebuilt revised page works.

The longer term solution is a complete in-house doc.  I have some ideas, which I will share later, for something more compact than the Shipman work (168 pages for the pdf).

Ned, a separate question is whether the link fix or a local replacement can be backported to 3.6.  It is like having half the tkinter doc, the part covering tk widgets, removed.