Description of problem:
I executed
sudo livecd-creator -c ~/iso/ks/spin-kickstarts/custom/qa-test-day.ks --releasever 18 --cache /var/cache/live

Version-Release number of selected component:
lorax-18.20-1.fc18

Additional info:
cmdline:        /usr/bin/python /sbin/mkefiboot -a /var/tmp/imgcreate-CYuBUc/iso-z2060w/EFI/BOOT /var/tmp/imgcreate-CYuBUc/iso-z2060w/isolinux/macboot.img -l 'Livecd Qa' -n /usr/share/pixmaps/bootloader/fedora-media.vol -i /usr/share/pixmaps/bootloader/fedora.icns -p 'Livecd Qa'
executable:     /sbin/mkefiboot
kernel:         3.6.7-4.fc17.x86_64
uid:            0

Truncated backtrace:
imgutils.py:137:umount:UnboundLocalError: local variable 'rv' referenced before assignment

Traceback (most recent call last):
  File "/sbin/mkefiboot", line 153, in <module>
    opt.diskname)
  File "/sbin/mkefiboot", line 44, in mkmacboot
    mkhfsimg(None, outfile, label=label, graft=graft, size=size)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 336, in mkhfsimg
    mkfsargs=["-v", label], graft=graft)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 319, in mkfsimage
    do_grafts(graft, mnt, preserve)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 234, in __exit__
    umount(self.mnt)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 137, in umount
    mnt, rv, count, maxretry)
UnboundLocalError: local variable 'rv' referenced before assignment

Local variables in innermost frame:
count: 1
lazy: False
mnt: '/tmp/lorax.imgutils.VEo66M'
retrysleep: 1.0
umount: ['umount', '/tmp/lorax.imgutils.VEo66M']
maxretry: 3