Delete the created network when subnet creation failed.

def _delete_network(self, request, network):
        """Delete the created network when subnet creation failed."""
        try:
            api.neutron.network_delete(request, network.id)
            LOG.debug('Delete the created network %s '
                      'due to subnet creation failure.', network.id)
            msg = _('Delete the created network "%s" '
                    'due to subnet creation failure.') % network.name
            redirect = self.get_failure_url()
            messages.info(request, msg)
            raise exceptions.Http302(redirect)
        except Exception as e:
            LOG.info('Failed to delete network %(id)s: %(exc)s',
                     {'id': network.id, 'exc': e})
            msg = _('Failed to delete network "%s"') % network.name
            redirect = self.get_failure_url()
            exceptions.handle(request, msg, redirect=redirect)