mozillaGH-36 Update RateLimitedCSPMiddleware to support csp_select de…

…corator

csp/contrib/rate_limiting.py

@@ -11,8 +11,10 @@ class RateLimitedCSPMiddleware(CSPMiddleware):
     to report-uri by excluding it from some requests."""
 
     def build_policy(self, request, response):
-        config = getattr(response, '_csp_config', None)
-        update = getattr(response, '_csp_update', None)
+        build_kwargs = {
+            key: getattr(response, '_csp_%s' % key, None)
+            for key in ('config', 'update', 'select')
+        }
         replace = getattr(response, '_csp_replace', {})
         nonce = getattr(request, '_csp_nonce', None)
 
@@ -21,5 +23,8 @@ def build_policy(self, request, response):
         if not include_report_uri:
             replace['report-uri'] = None
 
-        return build_policy(config=config, update=update, replace=replace,
-                            nonce=nonce)
+        return build_policy(
+            replace=replace,
+            nonce=nonce,
+            **build_kwargs,
+        )