[stable-only] Cap versions to allow CI to pass

New versions of virtualenv, tox, and setuptools break CI. Cap them.

Change-Id: I749d960381b7d2ab31947bbea8bdb9a24d54ec16

tox.ini

@@ -3,6 +3,10 @@ minversion = 3.18.0
 skipsdist = True
 envlist = py3,pep8
 ignore_basepython_conflict=true
+requires =
+  virtualenv<20.26.4
+  tox<4
+  setuptools<71
 
 [testenv]
 usedevelop = True
@@ -12,10 +16,14 @@ setenv = VIRTUAL_ENV={envdir}
          LANGUAGE=en_US
          LC_ALL=en_US.UTF-8
          PYTHONWARNINGS=default::DeprecationWarning
+# NOTE(JayF): New setuptools breaks installation, but we cannot restrict the version
+#             in requirements.txt without breaking the requirements check. Restricting
+#             it here instead.
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/yoga}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
+  setuptools<71
 commands =
     stestr run --slowest {posargs}
 passenv = http_proxy