code: def change_capacity_percent(self, group_name, scaling_adjustment):
          
          group = self.autoscaling_groups[group_name]
          percent_change = 1 + (scaling_adjustment / 100.0)
          desired_capacity = group.desired_capacity * percent_change
          if group.desired_capacity < desired_capacity < group.desired_capacity + 1:
              desired_capacity = group.desired_capacity + 1
          else:
              desired_capacity = int(desired_capacity)
          self.set_desired_capacity(group_name, desired_capacity)
docs: http://docs.aws.amazon.com/AutoScaling/latest/DeveloperGuide/as-scale-based-on-demand.html
          If PercentChangeInCapacity returns a value between 0 and 1,
          Auto Scaling will round it off to 1. If the PercentChangeInCapacity
          returns a value greater than 1, Auto Scaling will round it off to the
          lower value. For example, if PercentChangeInCapacity returns 12.5,
          then Auto Scaling will round it off to 12.