This TODO can't/shouldn't be done

Would have to forego the code-cleanliness of calling Song.to_dict in
order to cache a pre-made Event dict, and hack in user rating grabbing
into the process, pulling code from other parts of the project.
Added redownload M3U warning
Load election history on startup cache miss
Finish request-related TODOs

- Re-enabled checking randomly selected song for request status
- Moved request line re-entry to election start instead of election
creation
Remove request rank, add request_at_count code
Catch Pg transaction rollback errors