use customized constance (#4191)

thirdpart/constance/context_processors.py

@@ -0,0 +1,15 @@
+import constance
+
+
+def config(request):
+    """
+    Simple context processor that puts the config into every
+    RequestContext. Just make sure you have a setting like this:
+
+        TEMPLATE_CONTEXT_PROCESSORS = (
+            # ...
+            'constance.context_processors.config',
+        )
+
+    """
+    return {"config": constance.config}