'Notify all mechanism drivers during network creation.
:raises: DB retriable error if create_network_precommit raises them
See neutron.db.api.is_retriable for what db exception is retriable
or neutron.plugins.ml2.common.MechanismDriverError
if any mechanism driver create_network_precommit call fails.
Called within the database transaction. If a mechanism driver
raises an exception, then a MechanismDriverError is propagated
to the caller, triggering a rollback. There is no guarantee
that all mechanism drivers are called in this case.'

def create_network_precommit(self, context):

    self._check_vlan_transparency(context)
    self._call_on_drivers('create_network_precommit', context, raise_db_retriable=True)
