Currently failing with
error: cannot coerce a set to a string: { __functionArgs = «thunk»; __functor = «thunk»; }
This comes from the `extraTests` option I added to the test modules to
compose certain tests a little nicer. It's of type
either (functionTo ...) str
and it seems like the `functionTo` part now returns a functor (i.e. an
attr-set that can be invoked as function). This is caught by
`lib.isFunction`, but `builtins.isFunction` returns `false`.
Hence, switching to the former fixes this.
ad175bca29