guard_against_missing_reflections

# File activerecord/lib/active_record/associations.rb, line 893
        def guard_against_missing_reflections(reflections, options)
          reflections.each do |r| 
            raise(
              ConfigurationError, 
              "Association was not found; perhaps you misspelled it?  " +
              "You specified :include => :#{[options[:include]].flatten.join(', :')}"
            ) if r.nil? 
          end
        end