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

pycodestyle does not know about "importutils.try_import"
calls, so we have to either
  a) put them inside a "try" block
or
  b) add "# noqa: E402" to each import after the
     try_import call

Change-Id: Ia545bb689cfdfb57962d74e3957dfb372fd3782b

This removes some code that was still pointing to the V1 API. No need to
add release note or additional announcements since this was all removed
long ago, and if anyone would have gone down this code path it would
have just blown up trying to import the v1 code that is no longer there.

Change-Id: I7d239d3fe3d879e4c391e83cae1e394cf1f5e6eb
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

The __future__ module [1] was used in this context to ensure compatibility
between python 2 and python 3.

We previously dropped the support of python 2.7 [2] and now we only support
python 3 so we don't need to continue to use this module and the imports
listed below.

Imports commonly used and their related PEPs:
- `division` is related to PEP 238 [3]
- `print_function` is related to PEP 3105 [4]
- `unicode_literals` is related to PEP 3112 [5]
- `with_statement` is related to PEP 343 [6]
- `absolute_import` is related to PEP 328 [7]

[1] https://docs.python.org/3/library/__future__.html
[2] https://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html
[3] https://www.python.org/dev/peps/pep-0238
[4] https://www.python.org/dev/peps/pep-3105
[5] https://www.python.org/dev/peps/pep-3112
[6] https://www.python.org/dev/peps/pep-0343
[7] https://www.python.org/dev/peps/pep-0328

Change-Id: Id785793c36b3a6819a7522525252c3fef15ebe2b

The --bypass-url argument was removed with
I3b951cc4eb3adff23f3d2cbe674971816261ef56 so this name does not make
sense now.  Replace with os_endpoint.

Change-Id: Ifa889cc2e885e9c621c8494995b2020195b696ca

This tests that the expected subcommands register
in the shell client, by looking at the output
that would show up in "cinder help".

The purpose of this is to help prevent us from
accidentally deleting some commands when refactoring
shell code.

TODO: cover commands post-3.0
Change-Id: Ifcbc08ae9184fa33049b18f8ad7ef5d92003a7b8