requires_sudo?

# File lib/bundler.rb, line 354
    def requires_sudo?
      return @requires_sudo if defined?(@requires_sudo_ran)

      sudo_present = which "sudo" if settings.allow_sudo?

      if sudo_present
        # the bundle path and subdirectories need to be writable for RubyGems
        # to be able to unpack and install gems without exploding
        path = bundle_path
        path = path.parent until path.exist?

        # bins are written to a different location on OS X
        bin_dir = Pathname.new(Bundler.system_bindir)
        bin_dir = bin_dir.parent until bin_dir.exist?

        # if any directory is not writable, we need sudo
        files = [path, bin_dir] | Dir[bundle_path.join("build_info/*").to_s] | Dir[bundle_path.join("*").to_s]
        unwritable_files = files.reject {|f| File.writable?(f) }
        sudo_needed = !unwritable_files.empty?
        if sudo_needed
          Bundler.ui.warn "Following files may not be writable, so sudo is needed:\n  #{unwritable_files.map(&:to_s).sort.join("\n  ")}"
        end
      end

      @requires_sudo_ran = true
      @requires_sudo = settings.allow_sudo? && sudo_present && sudo_needed
    end