Description of problem:

When trying to create a kvm guest I get an error from virt-manager, that it couldn't create the guest.

Python backtrace:
Unable to complete install: 'Unable to create cgroup for F15_gw: No such file or directory'
Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 45, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/create.py", line 1643, in do_install
    guest.start_install(False, meter=meter)
  File "/usr/lib/python2.7/site-packages/virtinst/Guest.py", line 1187, in start_install
    start_xml, final_xml, is_initial)
  File "/usr/lib/python2.7/site-packages/virtinst/Guest.py", line 1246, in _create_guest
    dom = self.conn.createLinux(start_xml or final_xml, 0)
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 1346, in createLinux
    if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self)
libvirtError: Unable to create cgroup for F15_gw: No such file or directory

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

Latest in F15 fedora/updates repo's


How reproducible:

Every time

Steps to Reproduce:
1. create a guest.
2. click "Finish".
3. the creation starts, but fails.
  
Actual results:
Creation of the guest fails

Expected results:
Creation of the guest

Additional info: