Leagues.fetch_leagues_from_webapi sending unexpected keyword argument 'ignore_expiry'

[rjackson]

https://app.getsentry.com/arcanaio/pubstompinfo/group/23741048/

It's using the expired-cache-fallback facility which exists with Dotabank's custom filesystem cache: https://github.com/Arcana/dotabank-web/blob/master/app/cache.py#L23

We can either use Dotabank's cache here, or just skip on errors. Unlike Dotabank, we're persisting league data to a database - so it's not critical that we can always retrieve data from the WebAPI (whereas it is critical on Dotabank). Best solution is probably just skipping on errors.