Support tox4

Change-Id: If3a7005dc896ddf7c2556507f402c75a989551e2

tox.ini

@@ -1,7 +1,6 @@
 [tox]
 minversion = 3.18.0
-envlist = py38,pep8
-skipsdist = True
+envlist = py38,pep8,docs
 ignore_basepython_conflict = True
 
 [testenv]
@@ -17,15 +16,15 @@ deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
-allowlist_externals = sh
+allowlist_externals = bash
 commands =
   stestr run {posargs}
 
 [testenv:pep8]
 commands =
   flake8
-  {toxinidir}/tools/check_samples.sh
-  sh ./tools/coding-checks.sh --pylint '{posargs}'
+  bash {toxinidir}/tools/check_samples.sh
+  bash ./tools/coding-checks.sh --pylint '{posargs}'
   {[testenv:bandit]commands}
 
 [testenv:releasenotes]
@@ -91,7 +90,7 @@ commands = oslo_debug_helper -t neutron_lib/tests/unit {posargs}
 
 [testenv:api-report]
 commands =
-   {toxinidir}/tools/api_report.sh
+   bash {toxinidir}/tools/api_report.sh
 
 [flake8]
 # H106: Don't put vim configuration in source files
@@ -99,7 +98,7 @@ commands =
 # H204: Use assert(Not)Equal to check for equality
 # H205: Use assert(Greater|Less)(Equal) for comparison
 # H904: Delay string interpolations at logging calls
-enable-extensions=H106,H203,H204,H205,H904
+enable-extensions = H106,H203,H204,H205,H904
 show-source = True
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build,tools
 import-order-style = pep8