Dropping lower constraints testing

We facing errors related to the new pip resolver, this
topic was discussed on the ML and QA team proposed to
to test lower-constraints [1].

I propose to drop this test because the complexity and recurring pain needed
to maintain that now exceeds the benefits provided by this mechanismes.

Replace assertTrue by assertIn to fix with the latest flake8 version.
Add six in the documentation requirements to fix the build.
Fix the conflict status with hacking.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2020-December/019390.html

Change-Id: I580da15fefd6ad352e69749b77cc4664aef84f9c

1 files changed, 0 insertions, 5 deletions

diff --git a/tox.ini b/tox.ini
index f4f3fa1..549dd4e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -53,8 +53,3 @@ commands =
 ignore = W504
 exclude = .venv,.tox,dist,doc,*.egg,build
 show-source = true
-
-[testenv:lower-constraints]
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt