Merge pull request #2113 from edx/db/enable-theme-in-startup

Do theme post-processing in startup hook

lms/templates/main.html

@@ -8,7 +8,7 @@
 ## templates have access to these functions, and we can import these
 ## into non-inheriting templates via the %namespace tag.
 <%def name="theme_enabled()">
-  <% return settings.FEATURES["USE_CUSTOM_THEME"] %>
+  <% return settings.FEATURES.get("USE_CUSTOM_THEME", False) %>
 </%def>
 
 <%def name="stanford_theme_enabled()">