depend_on

# File activesupport/lib/active_support/dependencies.rb, line 315
    def depend_on(file_name, message = "No such file to load -- %s.rb")
      path = search_for_file(file_name)
      require_or_load(path || file_name)
    rescue LoadError => load_error
      if file_name = load_error.message[/ -- (.*?)(\.rb)?$/, 1]
        load_error.message.replace(message % file_name)
        load_error.copy_blame!(load_error)
      end
      raise
    end