verify_trust_dir (Gem::Security)

    # File lib/rubygems/security.rb, line 623
      def self.verify_trust_dir(path, perms)
        # if the directory exists, then make sure it is in fact a directory.  if
        # it doesn't exist, then create it with the appropriate permissions
        if File.exist?(path)
          # verify that the trust directory is actually a directory
          unless File.directory?(path)
            err = "trust directory #{path} isn't a directory"
            raise Gem::Security::Exception, err
          end
        else
          # trust directory doesn't exist, so create it with permissions
          FileUtils.mkdir_p(path)
          FileUtils.chmod(perms, path)
        end
      end