Comment 1 for bug 1206948

Looks like the xenapi driver is unable to get the product version from the host and when that happens there is no warning logged or anything, None is just returned:

https://github.com/openstack/nova/blob/master/nova/virt/xenapi/driver.py#L688

That sets the var that is passed to utils.convert_version_to_int.

I'm not sure why the driver can't get the product version from the host since I don't know much about the xenapi driver.