add sphinx_rtd_theme to extensions

Author: yomguy

.readthedocs.yml

@@ -20,6 +20,5 @@ formats: all
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-  version: 3.7
   install:
     - requirements: docs/requirements-docs.txt

docs/source/conf.py

@@ -29,7 +29,8 @@
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.autodoc',
+extensions = ['sphinx_rtd_theme',
+              'sphinx.ext.autodoc',
               'sphinx.ext.coverage',
               'sphinx.ext.viewcode',
               'sphinx.ext.autosummary',