Update the constraints url

For more detail, see http://lists.openstack.org/pipermail/openstack-discuss/2019-May/006478.html

Change-Id: I90662a9816c4f4af5a4a481d0e815bf6a398f8d3

tox.ini

@@ -18,7 +18,7 @@ setenv =
    OS_STDERR_CAPTURE=1
    OS_TEST_TIMEOUT=60
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
 commands = stestr run {posargs}
@@ -37,7 +37,7 @@ commands =
 [testenv:venv]
 basepython = python3
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/doc/requirements.txt
 commands = {posargs}
@@ -60,7 +60,7 @@ commands =
 # Molecule only supports python 2.7 and 3.6.
 basepython = python2
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/doc/requirements.txt
 whitelist_externals =
@@ -113,7 +113,7 @@ commands =
 [testenv:docs]
 basepython = python3
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
@@ -125,7 +125,7 @@ commands = oslo_debug_helper {posargs}
 [testenv:releasenotes]
 basepython = python3
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
+    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/doc/requirements.txt
 commands =