Drop tox.ini

This project uses nox for testing, which relies on a separate
config. Having two files specify the same things in different
formats is a recipe for future divergence.

Move the flake8 config section to a dedicated .flake8 file instead.

Update contributing instructions accordingly, and switch one
remaining tox-based job over to its nox equivalent.

Change-Id: Idfe4b0434436b48e13a4d2b2996c80de61deec49

.flake8

@@ -0,0 +1,6 @@
+[flake8]
+# E123, E125 skipped as they are invalid PEP-8.
+show-source = True
+ignore = E123,E125,E129,H,W503,W504
+builtins = _
+exclude=.venv,.git,.nox,.tox,dist,doc,*lib/python*,*egg,build

.zuul.yaml

@@ -60,4 +60,4 @@
     release:
       jobs:
         - opendev-release-python
-        - opendev-publish-unversioned-tox-docs
+        - opendev-publish-unversioned-nox-docs

CONTRIBUTING.rst

@@ -20,13 +20,13 @@ tools, or review ``bindep.txt`` by hand.
 Running Tests
 -------------
 
-The testing system is based on a combination of tox and testr. The canonical
-approach to running tests is to simply run the command `tox`. This will
+The testing system is based on a combination of nox and testr. The canonical
+approach to running tests is to simply run the command `nox`. This will
 create virtual environments, populate them with dependencies and run all of
-the tests that OpenStack CI systems run. Behind the scenes, tox is running
+the tests that OpenStack CI systems run. Behind the scenes, nox is running
 `testr run --parallel`, but is set up such that you can supply any additional
-testr arguments that are needed to tox. For example, you can run:
-`tox -- --analyze-isolation` to cause tox to tell testr to add
+testr arguments that are needed to nox. For example, you can run:
+`nox -- --analyze-isolation` to cause nox to tell testr to add
 --analyze-isolation to its argument list.
 
 It is also possible to run the tests inside of a virtual environment
@@ -39,6 +39,6 @@ test-requirements.txt. Installing them via pip, for instance, is simply::
 
 In you go this route, you can interact with the testr command directly.
 Running `testr run` will run the entire test suite. `testr run --parallel`
-will run it in parallel (this is the default incantation tox uses.) More
+will run it in parallel (this is the default incantation nox uses.) More
 information about testr can be found at:
 https://testrepository.readthedocs.io/en/latest/

tox.ini

@@ -1,42 +0,0 @@
-[tox]
-min_version = 3.1
-envlist = py3,pep8
-ignore_basepython_conflict=true
-
-[testenv]
-usedevelop = True
-basepython = python3
-install_command = pip install -U {opts} {packages}
-setenv = VIRTUAL_ENV={envdir}
-deps =
-  -r{toxinidir}/requirements.txt
-  -r{toxinidir}/test-requirements.txt
-commands =
-  stestr run {posargs}
-  stestr slowest
-
-[testenv:pep8]
-basepython = python3
-deps =
-  hacking>=7,<8
-commands = flake8
-
-[testenv:venv]
-commands = {posargs}
-
-[testenv:cover]
-setenv =
-  {[testenv]setenv}
-  PYTHON=coverage run --source bindep --parallel-mode
-commands =
-  stestr run {posargs}
-  coverage combine
-  coverage html -d cover
-  coverage xml -o cover/coverage.xml
-
-[testenv:docs]
-deps =
-  -r{toxinidir}/requirements.txt
-  -r{toxinidir}/doc/requirements.txt
-commands =
-  sphinx-build -W -d doc/build/doctrees -b html doc/source/ doc/build/html