Our Core API is starting to become quite cluttered with old deprecated APIs that we need to remove to make the API easier to use correctly. In additon, removing the old @property APIs will lead to some performance improvements, given the way Pykka proxies currently accesses the properties when inspecting the actor's interface.
Before we can remove the deprecated core APIs, we need to stop using them. Luckily, none of the WebSocket API based clients have ever had access to the deprecated properties, reducing the scope of this a great deal.
Update Mopidy tests to not use deprecated APIs. See #1083.
Review Mopidy itself for deprecated API use. For example by removing the deprecated Core APIs, then running automated and manual tests.