./example.rb:42: Use RbConfig instead of obsolete and deprecated Config. When running. Any insight to this?

example.rb

class Magical
  def power
		puts 'certain power a magical being would have'
	end
end

class Wizard < Magical
	def power
		puts 'The Ground Starts to Shake'
	end
end

class Dragon < Magical
	def power
		puts 'Flames Appear All Around'
	end
end

class Person
	attr_accessor :name
	def initialize(name)
		@dead = false
		@name = name
	end

	def kill!(by = nil)
		puts "No one dares mess with me,  #{name}"
		puts "Oh, no! My only weakness, a #{by.class}" if by
		puts
		@dead = true
	end

	def dead?
		@dead
	end
end

module Fight
	def self.apply_to_all_magicals
		magical_classes = Module.constants.map { |x|
			Module.const_get(x) }.select { |x|
				x.respond_to?(:superclass) && x.superclass == Magical }
			magical_classes.each do |magical_class|
				magical_class.module_eval do
					include Fight
				end
			end
	end

	def battle(person)
		power
		puts "The Sky Goes Grey, Ominious Music is Heard"
		person.kill!(self)
		power
		puts
	end
end

wizard = Wizard.new
dragon = Dragon.new
people = [Person.new('The Great and Powerful Fred'), Person.new('The Not So Great and Way Less Powerful Ted')]
begin
	wizard.battle(people[0])
rescue => e
	puts 'I can defeat anything, well except for my one weakness...'
end

begin
	dragon.battle(people[0])
rescue => e
	puts "No one shall know my one weakness"
end
puts

# not so fast
Fight.apply_to_all_magicals
wizard.battle(people[0])
dragon.battle(people[1])