Fix delete cache so it also deletes location with run = None.

common/djangoapps/cache_toolbox/core.py

@@ -118,4 +118,9 @@ def get_cached_content(location):
 
 
 def del_cached_content(location):
-    cache.delete(unicode(location).encode("utf-8"))
+    # delete content for the given location, as well as for content with run=None.
+    # it's possible that the content could have been cached without knowing the
+    # course_key - and so without having the run.
+    cache.delete_many(
+        [unicode(loc).encode("utf-8") for loc in [location, location.replace(run=None)]]
+    )