Basically, raise some comments from the _tkinter.c
module to the library reference:

   If Tcl is threaded, this approach won't work
anymore. The Tcl interpreter is only valid in the
thread that created it, and all Tk activity must happen
in this thread, also. That means that the mainloop must
be invoked in the thread that created the interpreter.
Invoking commands from other threads is possible;
_tkinter will queue an event for the interpreter
thread, which will then execute the command and pass
back the result. If the main thread is not in the
mainloop, and invoking commands causes an exception; if
the main loop is running but not processing events, the
command invocation will block.

Is this still valid (or has something already been added)?
If so, do you still think it is needed (we seem to have gotten along without it for 7 years)?
If so, will you rewrite the snippet (it starts with with a dangling 'this') and specify where you would put it?

Response with reset this to open.

Closing this due to lack of activity.