Updates for caracal tox.ini

Update the tox.ini file(s) to use the constraints file from
zaza-openstack-tests.

Change-Id: I6d610f87d0cbae2918916db4e549aa7ceb75f6cd

build-requirements.txt

@@ -1,7 +0,0 @@
-# NOTES(lourot):
-# * We don't install charmcraft via pip anymore because it anyway spins up a
-#   container and scp the system's charmcraft snap inside it. So the charmcraft
-#   snap is necessary on the system anyway.
-# * `tox -e build` successfully validated with charmcraft 1.2.1
-
-cffi==1.14.6; python_version < '3.6'  # cffi 1.15.0 drops support for py35.

tox.ini

@@ -42,7 +42,9 @@ passenv =
     CS_*
     OS_*
     TEST_*
-deps = -r{toxinidir}/test-requirements.txt
+deps =
+    -c {env:TEST_CONSTRAINTS_FILE:https://raw.githubusercontent.com/openstack-charmers/zaza-openstack-tests/master/constraints/constraints-2024.1.txt}
+    -r{toxinidir}/test-requirements.txt
 
 [testenv:py35]
 basepython = python3.5
@@ -133,7 +135,7 @@ commands = {posargs}
 
 [testenv:build]
 basepython = python3
-deps = -r{toxinidir}/build-requirements.txt
+deps =
 # NOTE(lourot): charmcraft 1.0.0 used to generate
 # nova-compute-nvidia-vgpu.charm, which is the behaviour expected by OSCI.
 # However charmcraft 1.2.1 now generates