process_iteration (Capistrano::Processable)

    # File lib/capistrano/processable.rb, line 16
        def process_iteration(wait=nil, &block)
          ensure_each_session { |session| session.preprocess }

          return false if block && !block.call(self)

          readers = sessions.map { |session| session.listeners.keys }.flatten.reject { |io| io.closed? }
          writers = readers.select { |io| io.respond_to?(:pending_write?) && io.pending_write? }

          if readers.any? || writers.any?
            readers, writers, = IO.select(readers, writers, nil, wait)
          end

          if readers
            ensure_each_session do |session|
              ios = session.listeners.keys
              session.postprocess(ios & readers, ios & writers)
            end
          end

          true
        end