[DRE-maint] ruby-redis is marked for autoremoval from testing

[Debian testing autoremoval watch]

ruby-redis 3.1.0-1 is marked for autoremoval from testing on 2015-10-01

It is affected by these RC bugs:
796013: ruby-redis: FTBFS: [Redis::CannotConnectError] exception expected, not Class: <Errno::ENETUNREACH>