Modify the url of upper_constraints_file

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

Change-Id: I3811ffd422107dcf05f79fce01482e432aed0b5c

lower-constraints.txt

@@ -28,7 +28,7 @@ fixtures==3.0.0
 flake8==2.5.5
 futurist==1.6.0
 hacking==0.12.0
-horizon==14.0.0.0b2
+horizon==14.0.0.0b3
 idna==2.6
 imagesize==1.0.0
 iso8601==0.1.11

tox.ini

@@ -4,11 +4,12 @@ envlist = py37,py36,py27,pep8,py27dj19,py27dj110,py3-dj111
 skipsdist = True
 
 [testenv]
+install_command = pip install {opts} {packages}
 usedevelop = True
-install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt} {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
-deps = -r{toxinidir}/requirements.txt
+deps = -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+       -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = /bin/bash run_tests.sh -N --no-pep8 {posargs}