Add support for tox 4

Some random fixups to make it tox 4-compliant.

Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
Change-Id: Iea0a929bda37d748497e6fdd730767e25bd9a6dc

tox.ini

@@ -1,15 +1,12 @@
 [tox]
-minversion = 2.0
-envlist = py37,pep8
-skipsdist = True
+minversion = 3.0
+envlist = py3,pep8
 
 [testenv]
-usedevelop = True
-passenv = UPPER_CONSTRAINTS_FILE
-install_command = pip install -U {opts} {packages}
-basepython = python3
+usedevelop = true
+passenv =
+    TOX_CONSTRAINTS_FILE
 setenv =
-    VIRTUAL_ENV={envdir}
     LANG=en_US.UTF-8
     LANGUAGE=en_US:en
     LC_ALL=C
@@ -17,17 +14,18 @@ setenv =
     OS_STDERR_CAPTURE=1
     OS_TEST_TIMEOUT=60
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
-  -r{toxinidir}/requirements.txt
-  -r{toxinidir}/test-requirements.txt
-commands = stestr run {posargs}
-           stestr slowest
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -r{toxinidir}/requirements.txt
+    -r{toxinidir}/test-requirements.txt
+commands =
+    stestr run {posargs}
+    stestr slowest
 
 [testenv:pep8]
-usedevelop = False
-skip_install = True
+usedevelop = false
+skip_install = true
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     doc8
     hacking
     pygments
@@ -50,29 +48,23 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
-skip_install = True
+skip_install = true
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -W -d doc/build/doctrees -b html doc/source/ doc/build/html
 
 [testenv:releasenotes]
-skip_install = True
+skip_install = true
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/doc/requirements.txt
-commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+commands =
+    sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [flake8]
 show-source = True
 builtins = _
-exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build,releasenotes/source/conf.py
-
-
-[testenv:lower-constraints]
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt
+exclude = .venv,.git,.tox,dist,doc,*lib/python*,*egg,build,releasenotes/source/conf.py