Force constraints when installing a package during tox test

The tox deps option grants installation of single dependencies and
requirements, optionally pinned using constraints, before installing
a package, therefore not granting installation of the correct
constraint during the package installation.
To fix that tox 4.4.0 has introduced the constrain_package_deps
option [1]

[1] https://tox.wiki/en/4.12.1/faq.html#using-constraint-files

Change-Id: Ied659411bffb3f37e67523bc50a6a03b19cceef6

tox.ini

@@ -1,8 +1,9 @@
 [tox]
-minversion = 3.18.0
+minversion = 4.4.0
 envlist = py3,pep8
 
 [testenv]
+constrain_package_deps = true
 usedevelop = True
 deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
@@ -56,6 +57,7 @@ deps =
     hacking~=6.1.0 # Apache-2.0
     pycodestyle>=2.0.0,<3.0.0 # MIT
     doc8>=0.8.1 # Apache-2.0
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
 commands =
     flake8 ironic_inspector
     doc8 -e .rst -e .inc README.rst CONTRIBUTING.rst doc/source api-ref/source
@@ -134,4 +136,4 @@ deps = codespell
 # note(JayF): {posargs} lets us run `tox -ecodespell -- -w` to get codespell
 #             to correct spelling issues in our code it's aware of.
 commands =
-  codespell {posargs}
+  codespell {posargs}