Move to python3

[Nguyen Hai]

OpenStack community is moving to Python 3 as Python 2.7 is nearing its end of life. See https://wiki.openstack.org/wiki/Python3

Tacker currently still has some functions related to the old python version. Therefore, when we force to run python3 for testing, it creates some fails, for example, https://review.openstack.org/#/c/572984/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/758717

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/758772

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/758717
Committed: https://git.openstack.org/cgit/openstack/tacker/commit/?id=a3377de8719889401f6ea97fb0c74eae4aa5c2f0
Submitter: Zuul
Branch: master

commit a3377de8719889401f6ea97fb0c74eae4aa5c2f0
Author: Yasufumi Ogawa <email address hidden>
Date: Mon Oct 19 04:59:05 2020 +0000

    Drop most of six importings

    This update is to drop six, and also Python2 support. However, only
    `tacker/test/common/helpers.py` which defines a set of functions for
    Python2 is remained because `compact_byte()` is called from several test
    classes. Although it'is not so quite hard to drop, better to be done in
    another patch because so many changes shouldn't be included in a update.

    Here is a summary of changes.

    * Remove all six importing other than `helpers.py`.

    * Revise the order of importing modules becaseu it's checked strictly
      more in the recent pep8 test.

    * For the update, it removes a test `test_json_with_utf()` defined in
      `tacker/tests/unit/test_wsgi.py` because it's required only for Python2
      and can be skipped for Python3, so no need to keep anymore.

    * Remove six from `requirements.txt` and `lower-constraints.txt`.

    Partial-bug: #1778644

    Change-Id: Ib37fd00ab6836e4efc04d1c14c10f312379c7212
    Signed-off-by: Yasufumi Ogawa <email address hidden>

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/758772
Committed: https://git.openstack.org/cgit/openstack/tacker/commit/?id=4222140d1eacd8da90216fa3591d33cc830a1fcf
Submitter: Zuul
Branch: master

commit 4222140d1eacd8da90216fa3591d33cc830a1fcf
Author: Yasufumi Ogawa <email address hidden>
Date: Mon Oct 19 09:34:40 2020 +0000

    Remove test helpers for Python2

    As the last update for dropping Python2 support, remove helper functions
    introduced to run unittests on both of py2 and py3 with six.

    Closes-bug: #1778644

    Change-Id: Ie75879f33edeeaa94247fec2d665fd1a4266c700
    Signed-off-by: Yasufumi Ogawa <email address hidden>

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/tacker 5.0.0.0rc1 release candidate.