seems like a setuptools/buildout issue; I added some debug in out Travis build and it seems buildout is not downloading wheels:
UnsupportedWheel: zc.recipe.egg is in an unsupported or invalid wheel
https://travis-ci.org/plonegovbr/portal.buildout/jobs/293662255
seems a known issue:
the workaround is:
$pip install zc.recipe.egg --no-cache-dir