Fab as of v0.8 is designed to build Buster based v16.x builds.
Building for previous major versions is quite crippled and almost certainly completely broken.
The attached package is for installation on Stretch/v15.x (intended for install on TKLDev).
Currently a slightly older fab package built for install on Buster is hosted on the buster-testing
TurnKey apt repo. It will be updated soon and once deemed ready, will be migrated to buster main
.