I was just trying to export some EventHandlers prior to applying an Oracle bundle patch and encountered the following error:

WLSTException: MDS-01160: Expecting absolute document reference. Reference “/metadata/iam-features-OIMMigration/EventHandlers.xml” is a relative reference to the document.MDS-91009: Operation “exportMetadata” failure. Use dumpStack() to view the full stacktrace.

The reference in the error looked pretty absolute to me but upon further inspection of the metadata_files property there was a space after the comma.  I removed all of the spaces from the line and re-ran weblogicExportMetadata.sh; and voila no more error.