fix html_theme_path overriding previous definition of it

docs/conf.py

@@ -106,7 +106,7 @@ if not on_rtd:  # only import and set the theme if we're building docs locally
 #html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
-html_theme_path = ['_themes']
+#html_theme_path = ['_themes']
 
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".