move on_rtd check to top of module

docs/conf.py

@@ -6,6 +6,26 @@
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 sys.path.insert(0, os.path.abspath('..'))
 
+# 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') == 'True'
+if on_rtd:
+    html_theme = 'default'
+
+    from unittest.mock import MagicMock
+
+    class Mock(MagicMock):
+        @classmethod
+        def __getattr__(cls, name):
+            return MagicMock()
+
+    MOCK_MODULES = ['PyQt5']
+    sys.modules.update((mod_name, Mock()) for mod_name in MOCK_MODULES)
+
+else:
+    html_theme = 'sphinx_rtd_theme'
+
 from msl import qt
 
 # -- General configuration ------------------------------------------------
@@ -96,25 +116,6 @@
 
 # -- Options for HTML output ----------------------------------------------
 
-# 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') == 'True'
-if on_rtd:
-    html_theme = 'default'
-
-    from unittest.mock import MagicMock
-
-    class Mock(MagicMock):
-        @classmethod
-        def __getattr__(cls, name):
-            return MagicMock()
-
-    MOCK_MODULES = ['PyQt5']
-    sys.modules.update((mod_name, Mock()) for mod_name in MOCK_MODULES)
-
-else:
-    html_theme = 'sphinx_rtd_theme'
 
 # 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