docs: Update changelog with PR#840

docs/changelog.rst

@@ -18,6 +18,11 @@ v0.20.0 (UNRELEASED)
 - Add cover URL to all scanned files with MusicBrainz album IDs. (Fixes:
   :issue:`697`, PR: :issue:`802`)
 
+- Local library API: Implementors of :meth:`mopidy.local.Library.lookup` should
+  now return a list of :class:`~mopidy.models.Track` instead of a single track,
+  just like the other ``lookup()`` methods in Mopidy. For now, returning a
+  single track will continue to work. (PR: :issue:`840`)
+
 **MPD frontend**
 
 - In stored playlist names, replace "/", which are illegal, with "|" instead of

mopidy/local/__init__.py

@@ -100,8 +100,8 @@ class Library(object):
         Lookup the given URI.
 
         :param string uri: track URI
-        :rtype: List of :class:`~mopidy.models.Track` or single
-        :class:`~mopidy.models.Track` for backward compatibility
+        :rtype: list of :class:`~mopidy.models.Track` (or single
+            :class:`~mopidy.models.Track` for backward compatibility)
         """
         raise NotImplementedError