tox: Migrate to tox v4

The current v3 configuration worked just fine, but it's not longer
possible to share envdirs between testenvs and tox 4 only supports
Python 3, so the two settings related to these were useless. They are
removed and we also clean up the file while we're at it.

Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
Change-Id: I6eac3be7f37887d743d54171021521d4b1c70482

tox.ini

@@ -1,29 +1,28 @@
 [tox]
-minversion = 3.1.1
+minversion = 4.3.0
 envlist = py3,pep8,releasenotes
-ignore_basepython_conflict = True
 
 [testenv]
 usedevelop = True
-setenv = VIRTUAL_ENV={envdir}
-         OS_STDOUT_NOCAPTURE=False
-         OS_STDERR_NOCAPTURE=False
+setenv =
+    OS_STDOUT_NOCAPTURE=False
+    OS_STDERR_NOCAPTURE=False
 deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/requirements.txt
-commands = stestr run {posargs}
 allowlist_externals =
-  bash
-basepython = python3
+    bash
+commands =
+    stestr run {posargs}
 
 [testenv:pep8]
 commands =
-  flake8
-  # Run security linter
-  # B110: except: pass
-  # B410: importing etree
-  bandit -r keystoneauth1 -x tests -s B110,B410
+    flake8
+    # Run security linter
+    # B110: except: pass
+    # B410: importing etree
+    bandit -r keystoneauth1 -x tests -s B110,B410
 
 [testenv:bandit]
 # NOTE(browne): This is required for the integration test job of the bandit
@@ -44,7 +43,41 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:debug]
-commands = oslo_debug_helper -t keystoneauth1/tests {posargs}
+commands =
+    oslo_debug_helper -t keystoneauth1/tests {posargs}
+
+[testenv:docs]
+setenv =
+    {[testenv]setenv}
+    SPHINX_APIDOC_OPTIONS=noindex,members,undoc-members,show-inheritance
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -r{toxinidir}/doc/requirements.txt
+commands =
+    bash -c "rm -rf doc/build"
+    bash -c "rm -rf doc/source/api"
+    sphinx-build -W -b html -d doc/build/doctrees doc/source doc/build/html
+
+[testenv:pdf-docs]
+setenv =
+    {[testenv]setenv}
+    SPHINX_APIDOC_OPTIONS=noindex,members,undoc-members,show-inheritance
+deps =
+    {[testenv:docs]deps}
+allowlist_externals =
+    make
+    rm
+commands =
+    rm -rf doc/build/pdf
+    sphinx-build -W -b latex doc/source doc/build/pdf
+    make -C doc/build/pdf
+
+[testenv:releasenotes]
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -r{toxinidir}/doc/requirements.txt
+commands =
+    sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [flake8]
 # D100: Missing docstring in public module
@@ -66,38 +99,6 @@ exclude = .venv,.tox,dist,doc,*egg,build
 import-order-style = pep8
 application-import-names = keystoneauth1
 
-[testenv:docs]
-setenv =
-    {[testenv]setenv}
-    SPHINX_APIDOC_OPTIONS=noindex,members,undoc-members,show-inheritance
-deps =
-    -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
-    -r{toxinidir}/doc/requirements.txt
-commands =
-    bash -c "rm -rf doc/build"
-    bash -c "rm -rf doc/source/api"
-    sphinx-build -W -b html -d doc/build/doctrees doc/source doc/build/html
-
-[testenv:pdf-docs]
-setenv =
-    {[testenv]setenv}
-    SPHINX_APIDOC_OPTIONS=noindex,members,undoc-members,show-inheritance
-envdir = {toxworkdir}/docs
-deps = {[testenv:docs]deps}
-allowlist_externals =
-  make
-  rm
-commands =
-  rm -rf doc/build/pdf
-  sphinx-build -W -b latex doc/source doc/build/pdf
-  make -C doc/build/pdf
-
-[testenv:releasenotes]
-deps =
-    -c{env:TOX_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
-    -r{toxinidir}/doc/requirements.txt
-commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
-
 [flake8:local-plugins]
 extension =
     K333 = checks:check_oslo_namespace_imports