tox 4 compatibility

Remove 'usedevelop = true' and 'skipsdist = true', the combination of
which now means we don't install dependencies. Also remove the
basepython setting, which is no longer needed since we don't have any
Python 2-first distros to worry about. Finally, remove the
lower-constraints job and we no longer test for these.

Change-Id: I5b4b8cc1facb6e18cf12d33ea8113d47a0a76235
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

.zuul.yaml

@@ -2,7 +2,6 @@
 - project:
     templates:
       - check-requirements
-      - openstack-lower-constraints-jobs
       - openstack-python3-antelope-jobs
       - osc-tox-unit-tips
       - publish-openstack-docs-pti

tox.ini

@@ -1,12 +1,8 @@
 [tox]
-minversion = 2.0
-envlist = py38,pep8
-skipsdist = True
-ignore_basepython_conflict = true
+minversion = 3.1
+envlist = py3,pep8
 
 [testenv]
-basepython = python3
-usedevelop = True
 setenv =
   OS_STDOUT_CAPTURE=1
   OS_STDERR_CAPTURE=1
@@ -15,8 +11,8 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
-commands = stestr run {posargs}
-whitelist_externals = stestr
+commands =
+  stestr run {posargs}
 
 [testenv:unit-tips]
 commands =
@@ -25,16 +21,17 @@ commands =
   python -m pip install -q -e "git+file://{toxinidir}/../openstacksdk#egg=openstacksdk"
   python -m pip freeze
   stestr run {posargs}
-whitelist_externals = stestr
 
 [testenv:pep8]
 deps =
   hacking>=3.0.1,<3.1.0 # Apache-2.0
   flake8-import-order>=0.17.1 # LGPLv3
-commands = flake8
+commands =
+  flake8
 
 [testenv:venv]
-commands = {posargs}
+commands =
+  {posargs}
 
 [testenv:cover]
 commands =
@@ -42,7 +39,8 @@ commands =
   coverage report
 
 [testenv:debug]
-commands = oslo_debug_helper -t osc_lib/tests {posargs}
+commands =
+  oslo_debug_helper -t osc_lib/tests {posargs}
 
 [testenv:docs]
 deps =
@@ -55,7 +53,11 @@ commands =
   sphinx-build -a -E -W -d doc/build/doctrees -b html doc/source doc/build/html
 
 [testenv:releasenotes]
-commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+deps =
+  -c{env:UPPER_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
 
 [flake8]
 show-source = True
@@ -66,9 +68,3 @@ ignore = W504
 import-order-style = pep8
 application-import-names = osc_lib
 filename = *.py
-
-[testenv:lower-constraints]
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt