"fix rtd theme

"

docs/conf.py

@@ -100,19 +100,10 @@
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 #
-on_rtd = os.environ.get("READTHEDOCS", None) == "True"
-
-if not on_rtd:  # only import and set the theme if we're building docs locally
-    try:
-        import sphinx_rtd_theme
-
-        html_theme = "sphinx_rtd_theme"
-        html_theme_path = [sphinx_rtd_theme.get_html_theme_path(), "."]
-    except:
-        html_theme = "default"
-        html_theme_path = ["."]
-else:
-    html_theme_path = ["."]
+import sphinx_rtd_theme
+
+html_theme = "sphinx_rtd_theme"
+html_theme_path = [sphinx_rtd_theme.get_html_theme_path(), "."]
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,