Make html fails
The following error shows up when running "make html" from a fresh environment:
Running Sphinx v2.3.1 loading pickled environment... done
Theme error: theme 'sphinx_mer_rtd_theme' doesn't have "theme" setting Makefile:20: recipe for target 'html' failed make: *** [html] Error 2
This error does not show when using a previous build of 'sphinx_mer_rtd_theme'.