+++ This bug was initially created as a clone of Bug #843452 +++

Created attachment 600486 [details]
Traceback

Description of problem:
When I schedule to provision machine with active MAC address, then I get the traceback (look at attachment) "The MAC address you entered is already in use by another active virtual machine." (after rhn_check on the client) and the incomprehensible message "Client execution returned "Fatal error in Python code occured [[6]]" (code -1)" (in WebUI).
This bug dependences on Bug 835791.

Version-Release number of selected component (if applicable):
spacewalk-java-1.7.54-89 (on Satellite)
spacewalk-koan-0.2.7-10 (on client)

How reproducible:
100% 

Steps to Reproduce:
1. We have got or we create a client with Virtualization Platform entitlements + at least one virtual guest on this client.
2. We create a kickstart profile
3. Schedule provisionig new virtual guest with kickstart profile, fill in "Guest Name", check "Begin kickstart at the next system check in" and click on "Advanced Configuration" button. 
4. Fill "MAC Address", use the same MAC address as have another active virtual guest on this client.

  
Actual results:
On client by rhn_check:
 - Traceback (look at attachment)
In WebUI schedule action detail:
 "Client execution returned "Fatal error in Python code occured [[6]]" (code -1)"


Expected results:
On client by rhn_check: 
 - Without traceback, only message "The MAC address you entered is already in use by another active virtual machine"
In WebUI schedule action detail:
 - Something as "Provisionig faild, The MAC address is already in use"