class Xcodeproj::Project::UUIDGenerator

def verify_no_duplicates!(all_objects, all_new_objects)
  duplicates = all_objects - all_new_objects
  UserInterface.warn "[Xcodeproj] Generated duplicate UUIDs:\n\n" <<
    duplicates.map { |d| "#{d.isa} -- #{@paths_by_object[d]}" }.join("\n") unless duplicates.empty?
end