# File lib/bundler/rubygems_integration.rb, line 585
    def redefine_method(klass, method, unbound_method = nil, &block)
      visibility = method_visibility(klass, method)
      begin
        if (instance_method = klass.instance_method(method)) && method != :initialize
          # doing this to ensure we also get private methods
          klass.send(:remove_method, method)
        end
      rescue NameError
        # method isn't defined
        nil
      end
      @replaced_methods[[method, klass]] = instance_method
      if unbound_method
        klass.send(:define_method, method, unbound_method)
        klass.send(visibility, method)
      elsif block
        klass.send(:define_method, method, &block)
        klass.send(visibility, method)
      end
    end