Description of problem:
When I have precreated partitioning with RAID1 thinPool and thinLV for root on it, the installation will fail with this exception.

How reproducible:
Always

Steps to reproduce:
1) Create partitioning before installation
	a) RAID1 thinPool with thinLV on it
2) Start the installation
3) Go to Manual partitioning
4) Use precreated partition thinLV for / (root mountpoint)
5) Start the installation

Actual result:
Exception will raise

Expected result:
Installation should be successful

Version-Release number of selected component:
anaconda-25.20.5-1

The following was filed automatically by anaconda:
anaconda 25.20.5-1 exception report
Traceback (most recent call first):
  File "/usr/lib/python3.5/site-packages/blivet/formats/__init__.py", line 558, in _pre_destroy
    raise DeviceFormatError("device path does not exist or is not writable")
  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 545, in destroy
    self._pre_destroy(**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/deviceaction.py", line 696, in execute
    self.format.destroy()
  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 325, 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 204, 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.DeviceFormatError: device path does not exist or is not writable

Additional info:
addons:         com_redhat_kdump, com_redhat_docker
cmdline:        /usr/bin/python3  /sbin/anaconda
cmdline_file:   initrd=/test/fedora_devel/initrd.img inst.stage2=ftp://cobra02/fedora_devel/ BOOT_IMAGE=/test/fedora_devel/vmlinuz 
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         4.8.4-301.fc25.x86_64
product:        Fedora
release:        Cannot get release name.
type:           anaconda
version:        25

Potential duplicate: bug 1379084