Remove PostgreSQL support in Neutron

[Rodolfo Alonso]

PostgreSQL support was deprecated for removal in Pike. [1] removes it from devstack and Neutron needs to remove it too.

FT and fullstack tests failing: [2][3]

[1] https://review.opendev.org/#/c/678496/
[2] https://678fd386f3c2a339f0e8-a75a90e4f62f1557c9429d321082a0da.ssl.cf2.rackcdn.com/689150/2/check/neutron-functional/346fed4/job-output.txt
[3] https://openstack.fortnebula.com:13808/v1/AUTH_e8fd161dc34c421a979a9e6421f823e9/zuul_opendev_logs_e21/689150/2/check/neutron-fullstack/e21acf8/job-output.txt

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/689215

[Hongbin Lu (hongbin.lu)]

Note: the gate failure looks intermittent

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

According to [1], the initial patch [2] was reverted.

There is a discussion in the community about this DB backend [3], so let's hold the patch in neutron [4]. I'll set the status to "Incomplete".

[1] https://review.opendev.org/#/c/689250/
[2] https://review.opendev.org/#/c/678496/
[3] https://review.opendev.org/#/c/490083/
[4] https://review.opendev.org/689215

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Just to document this bug:
- Revert "Remove deprecated PostgreSQL database driver": https://review.opendev.org/#/c/689250/
- Revert "Generate deprecation warning for postgresql": https://review.opendev.org/#/c/490083/
- Declare plainly the current state of PostgreSQL in OpenStack: https://review.opendev.org/#/c/427880/

There are some projects removing this DB backend from the CI. Neutron can decide to keep it for now or remove it from the CI.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Rodolfo Alonso Hernandez (<email address hidden>) on branch: master
Review: https://review.opendev.org/689215
Reason: If we need this patch at some point, we can resuscitate it.

For now, the community will be testing PostgreSQL in the CI.

[Slawek Kaplonski (slaweq)]

We have just one job with postgresql in the periodic queue and I think we can keep it like that. I'm closing that bug for now.