Update TOX_CONSTRAINTS_FILE for stable/yoga

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/yoga branch, tests will
continue to use the upper-constraints list on master.

Change-Id: Ic8efc084652559831be5f00710b7a7061872947f

tox.ini

@@ -8,7 +8,7 @@ usedevelop = True
 basepython = python3
 setenv = VIRTUAL_ENV={envdir}
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/yoga}
   -r{toxinidir}/test-requirements.txt
   .[ldap,memcache,mongodb]
 commands =
@@ -42,7 +42,7 @@ passenv = FAST8_NUM_COMMITS
 # NOTE(browne): This is required for the integration test job of the bandit
 # project. Please do not remove.
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/yoga}
   -r{toxinidir}/requirements.txt
   .[bandit]
 commands = bandit -r keystone -x 'keystone/tests/*'
@@ -84,7 +84,7 @@ passenv =
 
 [testenv:functional]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/yoga}
   -r{toxinidir}/test-requirements.txt
 setenv = OS_TEST_PATH=./keystone/tests/functional
 commands =
@@ -122,7 +122,7 @@ max-complexity=24
 
 [testenv:docs]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/yoga}
   -r{toxinidir}/doc/requirements.txt
   .[ldap,memcache,mongodb]
 commands=