```get_module_by_unique_id``` throws a ```KeyError``` if no module is found that has the matching unique key.  See https://github.com/dimagi/commcare-hq/commit/1284e1460c1dfe2f41ed2888cb1efcd4d51dc4f1#diff-535390eb5c83a4cd3449f82afd1fa9fbR2821