Comment 1 for bug 1416156

The fix for this is that the subnet-prefix-length should never be allowed to be more than what can be accommodated in the ip_pool. There is a TODO in the code for this:
https://github.com/stackforge/group-based-policy/blob/master/gbpservice/neutron/db/grouppolicy/group_policy_db.py#L1031-L1040