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 <yasufum.o@gmail.com>
a3377de871