Memoized runtime_env in order to prevent premature garbage collection of Env instance, which leads to pidfile getting deleted while resque-scheduler is still running.

The premature deletion of the pidfile, in my experience, happens on RedHat 5.5, but does not happen on RedHat 6.5.
I think you're missing an `||` here. I suppose you wanted to do the following:

    @runtime_env ||= Resque::Scheduler::Env.new(options)