https://github.com/h4ck3rm1k3/billy/blob/todo/billy/web/public/views/events.py#L57 because event is already a function name and this event variable shadows it.
billy/web/public/views/events.py:23: [W0621(redefined-outer-name), event_ical] Redefining name 'event' from outer scope (line 57)