Address DaveO's comments.

common/djangoapps/static_replace/__init__.py

@@ -163,8 +163,7 @@ def replace_static_urls(text, data_directory=None, course_id=None, static_asset_
         if settings.DEBUG and finders.find(rest, True):
             return original
         # if we're running with a MongoBacked store course_namespace is not None, then use studio style urls
-        elif (not static_asset_path) \
-                and course_id:
+        elif (not static_asset_path) and course_id:
             # first look in the static file pipeline and see if we are trying to reference
             # a piece of static content which is in the edx-platform repo (e.g. JS associated with an xmodule)
 

common/lib/xmodule/xmodule/modulestore/tests/test_mixed_modulestore.py

@@ -240,10 +240,11 @@ class CommonMixedModuleStoreSetup(CourseComparisonTest):
         return self.store.has_changes(self.store.get_item(location))
 
     # pylint: disable=dangerous-default-value
-    def _initialize_mixed(self, mappings={}, contentstore=None):
+    def _initialize_mixed(self, mappings=None, contentstore=None):
         """
         initializes the mixed modulestore.
         """
+        mappings = mappings or {}
         self.store = MixedModuleStore(
             contentstore, create_modulestore_instance=create_modulestore_instance,
             mappings=mappings,