Unhandled KeyError exception in get_images for relinked tracks

[kingosticks]

When a track is relinked, a different id is returned than what was used in the request.

Getting the images for "spotify:track:4nqN0p0FjfH39G3hxeuKad" contains the following in the response:

    "id" : "39S0DVDKeneEjsq4pV45PT",
    "linked_from" : {
      "external_urls" : {
        "spotify" : "https://open.spotify.com/track/4nqN0p0FjfH39G3hxeuKad"
      },
      "href" : "https://api.spotify.com/v1/tracks/4nqN0p0FjfH39G3hxeuKad",
      "id" : "4nqN0p0FjfH39G3hxeuKad",
      "type" : "track",
      "uri" : "spotify:track:4nqN0p0FjfH39G3hxeuKad"
    },

The relinked track has id "39S0DVDKeneEjsq4pV45PT" rather than "4nqN0p0FjfH39G3hxeuKad" and causes the following exception:

ERROR    2018-01-14 14:17:25,204 [11350:Core-15] mopidy.core.library
  SpotifyBackend backend caused an exception.
Traceback (most recent call last):
  File "/home/nick/Dev/mopidy-dev/mopidy/mopidy/core/library.py", line 19, in _backend_error_handling
    yield
  File "/home/nick/Dev/mopidy-dev/mopidy/mopidy/core/library.py", line 174, in get_images
    if future.get() is None:
  File "/home/nick/.virtualenvs/mopidy/local/lib/python2.7/site-packages/pykka/threading.py", line 52, in get
    compat.reraise(*self._data['exc_info'])
  File "/home/nick/.virtualenvs/mopidy/local/lib/python2.7/site-packages/pykka/compat.py", line 12, in reraise
    exec('raise tp, value, tb')
  File "/home/nick/.virtualenvs/mopidy/local/lib/python2.7/site-packages/pykka/actor.py", line 201, in _actor_loop
    response = self._handle_receive(message)
  File "/home/nick/.virtualenvs/mopidy/local/lib/python2.7/site-packages/pykka/actor.py", line 295, in _handle_receive
    return callee(*message['args'], **message['kwargs'])
  File "/home/nick/Dev/mopidy-dev/mopidy-spotify/mopidy_spotify/library.py", line 29, in get_images
    return images.get_images(self._backend._web_client, uris)
  File "/home/nick/Dev/mopidy-dev/mopidy-spotify/mopidy_spotify/images.py", line 39, in get_images
    result.update(_process_uris(web_client, uri_type, batch))
  File "/home/nick/Dev/mopidy-dev/mopidy-spotify/mopidy_spotify/images.py", line 75, in _process_uris
    uri = ids_to_uris[item['id']]

The above example track should demonstrate the problem regardless of where you are (i.e. all "markets") since it's apparently no longer available anywhere. The fix is probably just a case of using the id field from the linked_from section if it is defined.

[adamcik]

Following seems to do the trick, can make a proper PR later today.

diff --git a/mopidy_spotify/images.py b/mopidy_spotify/images.py
index 9d8b90b..7bcfee2 100644
--- a/mopidy_spotify/images.py
+++ b/mopidy_spotify/images.py
@@ -77,7 +77,12 @@ def _process_uris(web_client, uri_type, uris):
     for item in data.get(uri_type + "s", []):
         if not item:
             continue
-        uri = ids_to_uris[item["id"]]
+
+        if "linked_from" in item:
+            uri = ids_to_uris[item["linked_from"]["id"]]
+        else:
+            uri = ids_to_uris[item["id"]]
+
         if uri["key"] not in _cache:
             if uri_type == "track":
                 album_key = _parse_uri(item["album"]["uri"])["key"]

[adamcik]

Should probably also test with the track that is gone everywhere and not found.