Description of problem:
Crash of the new installer (fedora 18) when software raid with LVM configured.
The following was filed automatically by anaconda:
anaconda 18.37.11 exception report
Traceback (most recent call first):
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devicetree.py", line 776, in addUdevMDDevice
    "devicetree as %s" % (name, device.name))
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devicetree.py", line 1067, in addUdevDevice
    device = self.addUdevMDDevice(info)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devicetree.py", line 1894, in _populate
    self.addUdevDevice(dev)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devicetree.py", line 1842, in populate
    self._populate()
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/__init__.py", line 428, in reset
    self.devicetree.populate(cleanupOnly=cleanupOnly)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/__init__.py", line 139, in storageInitialize
    storage.reset()
  File "/usr/lib64/python2.7/threading.py", line 504, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/threads.py", line 91, in run
    threading.Thread.run(self, *args, **kwargs)
DeviceTreeError: MD RAID device None already in devicetree as 126

Additional info:
cmdline:        /usr/bin/python  /sbin/anaconda --liveinst --method=livecd:///dev/mapper/live-osimg-min --lang en_US.UTF-8
cmdline_file:   initrd=initrd0.img root=live:UUID=B6CA-6099 rootfstype=vfat ro rd.live.image rhgb rd.luks=0 rd.md=0 rd.dm=0  BOOT_IMAGE=vmlinuz0 
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         3.6.10-4.fc18.x86_64
other involved packages: python-libs-2.7.3-13.fc18.x86_64
package:        anaconda-18.37.11-1.fc18.x86_64
packaging.log:  
product:        Fedora
release:        Fedora release 18 (Spherical Cow)
type:           libreport
version:        18