# File lib/em/deferrable.rb, line 60
60:     def errback &block
61:       return unless block
62:       if @deferred_status == :failed
63:         block.call(*@deferred_args)
64:       elsif @deferred_status != :succeeded
65:         @errbacks ||= []
66:         @errbacks.unshift block # << block
67:       end
68:     end