tox: Bump min_version to 4.3.0

tox 4 is significantly faster when it comes to creating virtualenvs and
is far better and detecting e.g. changes to requirements. tox 4.3.0
includes many of the fixes for bugs introduced by tox 4.0 and is a good
default candidate.

Change-Id: I0bb7f75ed3e03965ecd4d260c1299b46dcbf4b1b
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

tox.ini

@@ -1,15 +1,9 @@
 [tox]
-minversion = 3.18.0
+minversion = 4.3.0
 envlist = py3,pep8
-#skipsdist = True
-# Automatic envs (pyXX) will only use the python version appropriate to that
-# env and ignore basepython inherited from [testenv] if we set
-# ignore_basepython_conflict.
-ignore_basepython_conflict = True
 
 [testenv]
-usedevelop = True
+usedevelop = true
-basepython = python3
 setenv =
     OS_STDOUT_CAPTURE=1
     OS_STDERR_CAPTURE=1
@@ -18,8 +12,8 @@ deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/requirements.txt
-commands = stestr run {posargs}
+commands =
-allowlist_externals = stestr
+    stestr run {posargs}
 
 [testenv:pep8]
 deps =
@@ -62,7 +56,6 @@ commands =
     pythom -m pip install -q -e "git+file://{toxinidir}/../openstacksdk#egg=openstacksdk"
     python -m pip freeze
     stestr run {posargs}
-allowlist_externals = stestr
 
 [testenv:functional]
 setenv =
@@ -90,7 +83,8 @@ deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/doc/requirements.txt
-commands = {posargs}
+commands =
+    {posargs}
 
 [testenv:cover]
 setenv =
@@ -126,7 +120,7 @@ commands =
     sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [flake8]
-show-source = True
+show-source = true
 exclude = .venv,.git,.tox,dist,doc,*lib/python*,*egg,build,tools,releasenotes
 # E203 Black will put spaces after colons in list comprehensions
 # E501 Black takes care of line length for us