Hammerspoon 0.9.80 introduced a breaking API change related to window management (https://github.com/Hammerspoon/hammerspoon/issues/2517, jasonrudolph/keyboard#72). Since Hammerspoon regularly prompts users to upgrade, anyone who upgraded to the newer version of Hammerspoon was then unable to use Window Layout Mode in jasonrudolph/keyboard v5.0.0 and earlier.
To be compatible with Hammerspoon 0.9.80 and up, this release updates to the new API, but this change is incompatible with older versions of Hammerspoon (0.9.79 and earlier).
To upgrade to this release, upgrade to Hammerspoon 0.9.81 and then update your local checkout of jasonrudolph/keyboard:
$ cd ~/keyboard $ git fetch $ git checkout v6.0.0
Shout-out to @landongrindheim for the fix! (https://github.com/jasonrudolph/keyboard/pull/73) ⚡