def get_renewer(it)
      case it
      when Numeric, true, nil
        return it, nil
      else
        begin
          return it.renew, it
        rescue Exception
          return it, nil
        end
      end
    end
def get_renewer(it)
      case it
      when Numeric, true, nil
        return it, nil
      else
        begin
          return it.renew, it
        rescue Exception
          return it, nil
        end
      end
    end
Returns a valid argument to make_expires and the renewer or nil.

 Given +true+, +nil+, or Numeric, returns that value and +nil+ (no actual
 renewer).  Otherwise it returns an expiry value from calling +it.renew+
 and the renewer.