} catch (Exception e) {
            invalidMetadata(session, trace, metadata, repository, e);
            result.addException(e);
        }

        return (versioning != null) ? versioning : Versioning.newInstance();
    }

    private void invalidMetadata(
            RepositorySystemSession session,
            RequestTrace trace,
            Metadata metadata,
            ArtifactRepository repository,

     *
     * @param content
     * @param error
     */
    void debug(CharSequence content, Throwable error);

    /**
     * Send an exception to the user in the <b>debug</b> error level.<br>
     * The stack trace for this exception will be output when this error level is enabled.
     *
     * @param error
     */
    void debug(Throwable error);

    void debug(Supplier<String> content);

   * a request itself.
   *
   * @since 31.0
   */
  public static final String X_DEVICE_REQUESTED_WITH = "X-Device-Requested-With";
  /** The HTTP {@code X-Do-Not-Track} header field name. */
  public static final String X_DO_NOT_TRACK = "X-Do-Not-Track";
  /** The HTTP {@code X-Forwarded-For} header field name (superseded by {@code Forwarded}). */
  public static final String X_FORWARDED_FOR = "X-Forwarded-For";

    @CheckForNull private Iterator<? extends T> toRemove;

    /* The iterator currently returning elements. */
    private Iterator<? extends T> iterator;

    /*
     * We track the "meta iterators," the iterators-of-iterators, below.  Usually, topMetaIterator
     * is the only one in use, but if we encounter nested concatenations, we start a deque of

   * exception, every unchecked exception as an unchecked exception, and every error as an error. In
   * addition, the cause of any {@code ExecutionException} is wrapped in order to ensure that the
   * new stack trace matches that of the current thread.
   *
   * <p>Instances of {@code exceptionClass} are created by choosing an arbitrary public constructor