Allow looking up artwork by release group

Historically we'd just fail if the specific MB release did not have
artwork, but this is silly. If the release itself does not have artwork,
we should also check the release group failing.

vrobbler/apps/music/models.py

@@ -77,14 +77,38 @@ class Album(TimeStampedModel):
                 for t in self.track_set.all():
                     self.artists.add(t.artist)
 
-    def fetch_artwork(self):
-        if not self.cover_image:
-            try:
-                img_data = musicbrainzngs.get_image_front(self.musicbrainz_id)
-                name = f"{self.name}_{self.uuid}.jpg"
-                self.cover_image = ContentFile(img_data, name=name)
-            except musicbrainzngs.ResponseError:
-                logger.warning(f'No cover art found for {self.name}')
+    def fetch_artwork(self, force=False):
+        if not self.cover_image and not force:
+            if self.musicbrainz_id:
+                try:
+                    img_data = musicbrainzngs.get_image_front(
+                        self.musicbrainz_id
+                    )
+                    name = f"{self.name}_{self.uuid}.jpg"
+                    self.cover_image = ContentFile(img_data, name=name)
+                    logger.info(f'Setting image to {name}')
+                except musicbrainzngs.ResponseError:
+                    logger.warning(
+                        f'No cover art found for {self.name} by release'
+                    )
+
+            if not self.cover_image and self.musicbrainz_releasegroup_id:
+                try:
+                    img_data = musicbrainzngs.get_release_group_image_front(
+                        self.musicbrainz_releasegroup_id
+                    )
+                    name = f"{self.name}_{self.uuid}.jpg"
+                    self.cover_image = ContentFile(img_data, name=name)
+                    logger.info(f'Setting image to {name}')
+                except musicbrainzngs.ResponseError:
+                    logger.warning(
+                        f'No cover art found for {self.name} by release group'
+                    )
+            if not self.cover_image:
+                logger.debug(
+                    f"No cover art found for release or release group for {self.name}, setting to default"
+                )
+                # TODO Get a placeholder image in here
                 self.cover_image = 'default-image-replace-me'
             self.save()