For those keeping up with newer versions using Lingnik's patch (https://github.com/Robpol86/sphinxcontrib-versioning/pull/46): The signature of `sphinx.config.Config.__init__` changed in Sphinx 1.8. The fix is https://github.com/leokoppel/sphinxcontrib-versioning/commit/93fe26211de4322c0ddf347f51e095b580cdcd55.