As per victoria cycle testing runtime and community goal[1]
we need to migrate upstream CI/CD to Ubuntu Focal(20.04).
Fixing:
- bug#1886298
Bump the lower constraints for required deps which added python3.8 support
in their later version.
- pep8 error
- Set bionic nodeset for py36 and py37 job.
[1] https://governance.openstack.org/tc/goals/selected/victoria/migrate-ci-cd-jobs-to-ubuntu-fo$
Story: #2007865
Task: #40179
Change-Id: Ibab96807a7747738282732fe0069b9bc197da0ee