[sqlalchemy-20] Use the .begin() method of Engine

[Rodolfo Alonso]

Testing patch: https://review.opendev.org/c/openstack/neutron/+/874778

Logs: https://c06c4109be1832423601-1eb2471c773c922210e88856273ba212.ssl.cf5.rackcdn.com/874778/1/check/neutron-functional-with-uwsgi/4c704c1/job-output.txt

Error:
2023-02-22 20:05:33.640982 | controller | /home/zuul/src/opendev.org/openstack/neutron/neutron/tests/functional/db/test_migrations.py:422: RemovedIn20Warning: The current statement is being autocommitted using implicit autocommit, which will be removed in SQLAlchemy 2.0. Use the .begin() method of Engine or Connection in order to use an explicit transaction for DML and DDL statements. (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/874867

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/874867
Committed: https://opendev.org/openstack/neutron/commit/e7c92d92e479a4bdadb7e0a70305434ecd935fe7
Submitter: "Zuul (22348)"
Branch: master

commit e7c92d92e479a4bdadb7e0a70305434ecd935fe7
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Sat Feb 18 15:08:39 2023 +0100

    [sqlalchemy-20] Use the .begin() method of Engine

    Closes-Bug: #2008226
    Change-Id: Id713799a45b543edcdd3011444addaba9469bd61

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 22.0.0.0rc1 release candidate.