Description of problem:
Trying to configure a system with a RAID1 /boot and encrypted RAID1 / (no swap)
The following was filed automatically by anaconda:
anaconda 18.37.10 exception report
Traceback (most recent call first):
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/partitioning.py", line 1632, in __init__
    self.size = int(size / len(devices))
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/__init__.py", line 1984, in setContainerMembers
    size_set = factory.set_class(members, container_size)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/__init__.py", line 2167, in newDevice
    members=members, device=device)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/custom.py", line 1193, in _save_right_side
    raid_level=raid_level)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/custom.py", line 2481, in on_apply_clicked
    self._save_right_side(self._current_selector)
ZeroDivisionError: float division by zero

Additional info:
cmdline:        /usr/bin/python  /sbin/anaconda
cmdline_file:   initrd=initrd.img inst.stage2=hd:LABEL=Fedora\x2018\x20x86_64 quiet BOOT_IMAGE=vmlinuz 
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         3.6.10-4.fc18.x86_64
other involved packages: 
package:        anaconda-18.37.10
product:        Fedora
release:        Cannot get release name.
type:           libreport
version:        18