I noticed by accident that tests for software/wendelin/software-dev.cfg where failing because buildout was picking eggs:

Installing eggs.
While:
  Installing eggs.
  Getting distribution for 'scikit-learn'.
Error: Picked: scikit-learn = 0.19.2
Failed to run buildout profile in directory '/srv/slapgrid/slappart7/srv/testnode/acv/soft/78ae8a6d8b0639addb22de2c7c96af63'

Turned out it was a problem with usage of zc.recipe.egg:develop

There was also a problem which ${gcc-fortran:} that does not exist anymore.