Scikit-Image does not set or change the default value for this config parameter in our doc build - indeed, searching for latex_use_modeindex in our repo yields no results at all.

However, we require the doc build to complete without warnings. It seems with completely default settings, this is throwing a warning on Sphinx 1.5. As a result, all of our continuous integration builds are failing. The warning is thrown from this line in Sphinx.

See log here: https://travis-ci.org/scikit-image/scikit-image/jobs/182043593
In reference to recently merged PR scikit-image/scikit-image#2366, which passed with flying colors in the PR Travis build.