IDLE warns against an old TCL version even though I've installed a newer version

Question

I have installed ActiveTcl8.6.1.1.297588-macosx10.5-i386-x86_64-threaded on my OS X 10.9.1 . However, when I launch IDLE by running idle3 from the

Answer 1

This seems to be broken on High Sierra. After following the steps idle3 crashes when opening a file with "Invalid or prematurely freed autorelease pool" after issuing a warning that FIFinderSyncExtensionHost is installed in two places.