Description of problem:
Installing F25, ppc64 from nightly compose ISO doesn't succeed when "Encrypt my data" option is selected. Following are the steps to reproduce the problem:
1. Try to install Fedora 25 nightly compose using dvd ISO available at http://ppc.koji.fedoraproject.org/compose/branched/Fedora-25-20160907.n.0/compose/Server/ppc64/iso/ or from any previous nightly compose
2. In INSTALLATION DESTINATION, choose(select checkbox)  "Encrypt my data"
3. Enter Disk Encryption Passphrase when asked and then Begin Installation
4. Installation will stop in between during process of Creating luks on /dev/sda3

Version-Release number of selected component:
anaconda-25.20-1

The following was filed automatically by anaconda:
anaconda 25.20-1 exception report
Traceback (most recent call first):
  File "/usr/lib/python3.5/site-packages/blivet/formats/luks.py", line 221, in _setup
    raise LUKSError(e)
  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/formats/__init__.py", line 602, in setup
    self._setup(**kwargs)
  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/devices/storage.py", line 501, in setup_parents
    _format.setup()
  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/devices/storage.py", line 433, in _pre_create
    self.setup_parents()
  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/devices/storage.py", line 442, in create
    self._pre_create()
  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/deviceaction.py", line 318, in execute
    self.device.create()
  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/actionlist.py", line 322, in process
    action.execute(callbacks)
  File "/usr/lib/python3.5/site-packages/blivet/actionlist.py", line 48, in wrapped_func
    return func(obj, *args, **kwargs)
  File "/usr/lib/python3.5/site-packages/blivet/blivet.py", line 163, in do_it
    self.devicetree.actions.process(callbacks=callbacks, devices=self.devices)
  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/osinstall.py", line 1112, in turn_on_filesystems
    storage.do_it(callbacks)
  File "/usr/lib64/python3.5/site-packages/pyanaconda/install.py", line 200, in doInstall
    turn_on_filesystems(storage, mount_only=flags.flags.dirInstall, callbacks=callbacks_reg)
  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 251, in run
    threading.Thread.run(self, *args, **kwargs)
blivet.errors.LUKSError: Failed to activate device: Operation not permitted

Additional info:
addons:         com_redhat_kdump
cmdline:        /usr/bin/python3  /sbin/anaconda
cmdline_file:   BOOT_IMAGE=/ppc/ppc64/vmlinuz ro
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         4.8.0-0.rc4.git0.1.fc25.ppc64
product:        Fedora
release:        Cannot get release name.
type:           anaconda
version:        25