The UserRightsProxy was used to get/set groups for the users in foreign wikis. We need to remove all usages of this class, since now the correct way of accessing groups for users in the foreign wikis is to use UserGroupManagerFactory to create a manager pointing to the correct domain.
CodeSearch: https://codesearch.wmcloud.org/search/?q=UserRightsProxy&files=&excludeFiles=&repos=