# File lib/em/deferrable.rb, line 61
61:     def errback &block
62:       return unless block
63:       @deferred_status ||= :unknown
64:       if @deferred_status == :failed
65:         block.call(*@deferred_args)
66:       elsif @deferred_status != :succeeded
67:         @errbacks ||= []
68:         @errbacks.unshift block # << block
69:       end
70:     end