class ActiveSupport::EventedFileUpdateChecker

def directories_to_watch
  dtw = (@files + @dirs.keys).map { |f| @ph.existing_parent(f) }
  dtw.compact!
  dtw.uniq!
  normalized_gem_paths = Gem.path.map { |path| File.join path, "" }
  dtw = dtw.reject do |path|
    normalized_gem_paths.any? { |gem_path| path.to_s.start_with?(gem_path) }
  end
  @ph.filter_out_descendants(dtw)
end