Description of problem:
This is from the raid-1 kickstart test

Version-Release number of selected component:
anaconda-25.5-1

The following was filed automatically by anaconda:
anaconda 25.5-1 exception report
Traceback (most recent call first):
  File "/usr/lib/python3.5/site-packages/blivet/threads.py", line 45, in run_with_lock
    return m(*args, **kwargs)
  File "/usr/lib/python3.5/site-packages/blivet/blivet.py", line 842, in new_mdarray
    return MDRaidArrayDevice(name, *args, **kwargs)
  File "/usr/lib/python3.5/site-packages/blivet/threads.py", line 45, in run_with_lock
    return m(*args, **kwargs)
  File "/usr/lib64/python3.5/site-packages/pyanaconda/kickstart.py", line 1559, in execute
    request = storage.new_mdarray(**kwargs)
  File "/usr/lib64/python3.5/site-packages/pyanaconda/kickstart.py", line 1415, in execute
    r.execute(storage, ksdata, instClass)
  File "/usr/lib64/python3.5/site-packages/pyanaconda/kickstart.py", line 2211, in doKickstartStorage
    ksdata.raid.execute(storage, ksdata, instClass)
  File "/usr/lib64/python3.5/site-packages/pyanaconda/ui/gui/spokes/storage.py", line 353, in _doExecute
    doKickstartStorage(self.storage, self.data, self.instclass)
  File "/usr/lib64/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib64/python3.5/site-packages/pyanaconda/threads.py", line 253, in run
    threading.Thread.run(self, *args, **kwargs)
TypeError: __init__() got an unexpected keyword argument 'chunk_size'

Additional info:
addons:         com_redhat_kdump, com_redhat_docker
cmdline:        /usr/bin/python3  /sbin/anaconda
cmdline_file:   BOOT_IMAGE=vmlinuz initrd=initrd.img inst.stage2=hd:LABEL=Fedora-E-dvd-x86_64-rawh quiet ks=http://192.168.100.1/~dshea/raid-1.ks
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         4.6.0-0.rc1.git0.1.fc25.x86_64
product:        Fedora
release:        Cannot get release name.
type:           anaconda
version:        rawhide