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: If0abae9bbfabbd0cd2fb385b65e0eaeec8255df4

tox.ini

@@ -16,7 +16,7 @@ setenv =
 passenv = *_proxy *_PROXY
 
 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}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = find . -type f -name "*.pyc" -delete
@@ -31,7 +31,7 @@ commands = flake8
 [testenv:pylint]
 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}/requirements.txt
        pylint==1.9.1
 commands = bash tools/lintstack.sh
@@ -55,7 +55,7 @@ commands =
 [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}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -b html doc/source doc/build/html
@@ -63,7 +63,7 @@ commands = sphinx-build -b html doc/source doc/build/html
 [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}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html