Description of problem:
Launching Anaconda with the  2017-06-14 14:08    compose, pressing "Continue" on the first screen results in a traceback

Traceback (most recent call first):
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/__init__.py", line 180, in _findUIFile
    raise IOError("Could not load UI file '%s' for object '%s'" % (self.uiFile, self))
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/__init__.py", line 154, in __init__
    self.builder.add_objects_from_file(self._findUIFile(), self.builderObjects)
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/spokes/__init__.py", line 59, in __init__
    GUIObject.__init__(self, data)
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/spokes/installation_source.py", line 380, in __init__
    NormalSpoke.__init__(self, *args, **kwargs)
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/hubs/__init__.py", line 141, in _createBox
    spoke = spokeClass(self.data, self.storage, self.payload, self.instclass)
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/hubs/__init__.py", line 370, in refresh
    self._createBox()
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/__init__.py", line 1031, in _on_continue_clicked
    nextAction.refresh()
OSError: Could not load UI file 'spokes/source.glade' for object 'SourceSpoke'


Version-Release number of selected component (if applicable):
27.12-1

How reproducible:
Always

Steps to Reproduce:
1. As root

$ virt-install --location https://www.mirrorservice.org/sites/dl.fedoraproject.org/pub/fedora/linux//development/rawhide/Server/x86_64/os/ --name f27x86_64 --file /var/lib/libvirt/images/f27x86_64.img --file-size 20 --ram 4000 --vnc --noautoconsole

2. Connect to VNC server with virt-viewer/virt-manager
3. Press "Continue" on first screen

Actual results:
Kaboom with above traceback.

Expected results:
Can carry on with installer

Additional info: