Use upper constraints

Use upper constraints in the main [testenv] and in the docs build.

Change-Id: I3d696e7603f7d1aa56ac9546892a5930488e67be

tox.ini

@@ -6,7 +6,9 @@ skipsdist = True
 [testenv]
 install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
-deps = -r{toxinidir}/test-requirements.txt
+deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/test-requirements.txt
 passenv = GENERATE_GRENADE_PLUGIN_LIST
 
 [testenv:venv]
@@ -20,7 +22,9 @@ commands =
 [testenv:docs]
 basepython = python3
 whitelist_externals = bash
-deps = -r{toxinidir}/doc/requirements.txt
+deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/doc/requirements.txt
 setenv =
   TOP_DIR={toxinidir}
   INSTALL_SHOCCO=true