db_failover fails using Redis 3.0.1

[dv]

I'm using Redis 3.0.1. When a redis connection is refused, it throws a Redis::CannotConnectError exception, not a ECONNREFUSED exception, therefore it still bubbles upwards and kills the app.

I suggest using a catch-all exception handler when db_failover is enabled, since it's quite important for production systems to "keep calm and carry on" and I don't want to check all possible exceptions this and future Redis could throw (Timeout exceptions? Peer disconnected exceptions?).