Add debug to troubleshoot issue #38

app/model.py

@@ -317,10 +317,17 @@ class PlaylistTracks(Base):
         else:
             # Destination playlist has tracks; add to end
             new_row = max_row + 1
-        record = session.query(PlaylistTracks).filter(
-            PlaylistTracks.playlist_id == from_playlist_id,
-            PlaylistTracks.row == row
-        ).one()
+        try:
+            record = session.query(PlaylistTracks).filter(
+                PlaylistTracks.playlist_id == from_playlist_id,
+                PlaylistTracks.row == row).one()
+        except NoResultFound:
+            # Issue #38?
+            ERROR(
+                f"No rows matched in query: "
+                f"PlaylistTracks.playlist_id == {from_playlist_id}, "
+                f"PlaylistTracks.row == {row}"
+            )
         record.playlist_id = to_playlist_id
         record.row = new_row
         session.commit()