Comment 5 for bug 873686

The code we're talking about is:

    def lease_fixed_ip(self, context, address):
        fixed_ip = self.db.fixed_ip_get_by_address(context, address)

        if fixed_ip['instance_uuid'] is None:
            msg = _('IP %s leased that is not associated') % address
            raise exception.NovaException(msg)

This is called when dnsmasq leases out the IP address. There basically is no way for users to trigger this error and exceptions we throw from this method would just be logged to a log file.

InstanceNotFoundException is not appropriate. Something like FixedIpNotAssociated would be more accurate. But, again, since this is not an error ever seen by users, I think just using NovaException is fine.