Support for the Ruby 2.4 series has ended. See here for reference.
ImageBase
# File rss/maker/0.9.rb, line 225 def to_feed(rss) image = Rss::Channel::Image.new set = setup_values(image) if set image.link = link rss.channel.image = image set_parent(image, rss.channel) setup_other_elements(rss, image) elsif required_element? raise NotSetError.new("maker.image", not_set_required_variables) end end