index_logo is not a theme supported option

docs/conf.py

@@ -113,9 +113,7 @@
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-html_theme_options = {
-    'index_logo': None,
-}
+html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
 sys.path.append(os.path.abspath('_themes'))