Fix of tracback during SongPro import. Fixes bug 1582152. Fix traceback during songshowplus import. Fixes bug 1585489. Skip PresentationManager files we do not support." bzr-revno: 2677 Fixes: https://launchpad.net/bugs/1582152, https://launchpad.net/bugs/1585489, https://launchpad.net/bugs/1590657