Use upper-constraints in tox test environments

This will force pip install to use the upper-constraints.txt specified
version of pip modules. When you don't do this, you are out on the
bleeding edge and become unstable everytime some python library in the
wide world changes in a way that you don't expect.

The releasenotes job has no constraints file, so override the install
command there.

This commit is being proposed on stable/mitaka and therefore the
install command includes the clear designation of the branch. This is
because, on branches other than master, we need to be sure to get the
upper-constraints.txt file for that branch.

Change-Id: I5c2d878c79dcf1ce1715218950c07a39314b16ff
Partial-bug: #1598906

tox.ini

@@ -7,7 +7,7 @@ skipsdist = True
 setenv = VIRTUAL_ENV={envdir}
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 usedevelop = True
-install_command = pip install {opts} {packages}
+install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt?h=stable/mitaka} {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =
@@ -20,9 +20,17 @@ commands =
     flake8 {posargs}
 
 [testenv:venv]
+# NOTE(from nova tox.ini by jaegerandi): This target does not use constraints
+# because upstream infra does not yet support it. Once that's fixed, we can
+# drop the install_command.
+install_command = pip install -U --force-reinstall {opts} {packages}
 commands = {posargs}
 
 [testenv:cover]
+# NOTE(from nova tox.ini by jaegerandi): This target does not use constraints
+# because upstream infra does not yet support it. Once that's fixed, we can
+# drop the install_command.
+install_command = pip install -U --force-reinstall {opts} {packages}
 commands = python setup.py testr --coverage --testr-args='{posargs}'
 
 [testenv:docs]
@@ -36,6 +44,10 @@ commands = flake8
 commands = oslo-config-generator --config-file etc/oslo-config-generator/muranoagent.conf
 
 [testenv:releasenotes]
+# NOTE(from nova tox.ini by jaegerandi): This target does not use constraints
+# because upstream infra does not yet support it. Once that's fixed, we can
+# drop the install_command.
+install_command = pip install -U --force-reinstall {opts} {packages}
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [flake8]