Update UPPER_CONSTRAINTS_FILE for stable/stein

Update the URL to the upper-constraints file to point to the redirect
rule on releases.openstack.org so that anyone working on this branch
will switch to the correct upper-constraints list automatically when
the requirements repository branches.

Until the requirements repository has as stable/stein branch, tests will
continue to use the upper-constraints list on master.

Change-Id: I585b2aa33919472c66a10577866511ed07188f06

tox.ini

@@ -18,7 +18,7 @@ setenv =
 # clue for oslo.db to use file-based database.
   OS_TEST_DBAPI_ADMIN_CONNECTION=sqlite:////tmp/placeholder-never-created-nor-used.db
 usedevelop = True
-install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
+install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/stein} {opts} {packages}
 deps = -r{toxinidir}/test-requirements.txt
 commands =
     find . -type f -name "*.pyc" -delete
@@ -100,7 +100,7 @@ basepython = python3
 # This environment is called from CI scripts to test and publish
 # the API Ref to developer.openstack.org.
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/stein}
     -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf api-ref/build
@@ -137,7 +137,7 @@ import_exceptions = glance.i18n
 [testenv:docs]
 basepython = python3
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/stein}
     -r{toxinidir}/doc/requirements.txt
 commands =
   rm -fr doc/build
@@ -151,7 +151,7 @@ commands = {posargs}
 [testenv:releasenotes]
 basepython = python3
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/stein}
     -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html