Testing for bugs off master for opaque-keys deprecation

This pull request is to identify trouble spots after opaque-keys deprecation.
Yeah, we need to fix `PersistentCourseFactory` to no longer use `offering` anywhere. I've been focused on getting everything fixed in `common/lib/xmodule`, so those changes haven't bubbled into `cms` yet. Unfortunately, we started out at the top, before realizing that there was underlying stuff that needed to be fixed first.