Description of problem:
I tried to register system with Fedora 23 to Satellite and I received error from server side.

It is same issue as Bug 1309337 in Spacewalk


Version-Release number of selected component (if applicable):
spacewalk-backend-2.3.3-39.el6sat.noarch

How reproducible:
Always

Steps to Reproduce:
1. Install Fedora 23 and rhn-setup from spacewalk repository
2. Try to register system to Satellite 5.7

Actual results:
I received Internal Server Error.

AttributeError: 'Server' object has no attribute 'virt_uuid'

Expected results:
Registration is finished without error.

Additional info:
Exception reported from elisha.usersys.redhat.com
Time: Wed Apr  6 08:24:21 2016
Exception type <type 'exceptions.AttributeError'>
Exception while handling function registration.upgrade_version
Request object information:
URI: /XMLRPC
Remote Host: test01-64.sysmgmt.lab.eng.rdu2.redhat.com
Server Name: elisha.usersys.redhat.com:80
Headers passed in:
...

Exception Handler Information
Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/spacewalk/server/apacheRequest.py", line 122, in call_function
    response = func(*params)
  File "/usr/share/rhn/server/handlers/xmlrpc/registration.py", line 842, in upgrade_version
    server.save()
  File "/usr/lib/python2.6/site-packages/spacewalk/server/rhnServer/server_class.py", line 573, in save
    self.__save(channel)
  File "/usr/lib/python2.6/site-packages/spacewalk/server/rhnServer/server_class.py", line 551, in __save
    if self.virt_uuid is not None and \
AttributeError: 'Server' object has no attribute 'virt_uuid'