Fresh Plone 6 site broken with buildout.plonetest

My buildout uses

https://raw.githubusercontent.com/collective/buildout.plonetest/master/test-6.0.x.cfg

with in an add-on buildout.

A fresh Plone site is rendered with these JS errors...bug or feature?

I think that is what @mauritsvanrees means in this post:

Yesterday, i rollback all my dev packages to https://dist.plone.org/release/6.0.0a3/versions.cfg