Modify tox tests to respect upper-constraints.txt

This forces pip install to use the upper-constraints.txt specified
version of pip modules. Otherwise, the versions of the requirements
that are pulled are the most recent ones, which is not always
desired, e.g. for testing stable branches.

This change was inspired by Ie1133e4c020106e8098685ba9125f84b356d8e0c

Closes-Bug: #1563038
Change-Id: I921257a1e4cc3223878d3559af80410f24313425
(cherry picked from commit 9ca366f843ab9ddeb0050c1009634903d2fde29d)

tox.ini

@@ -2,7 +2,7 @@
 envlist = pep8,py34,py27,docs
 
 [testenv]
-install_command = pip install -U {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
 
@@ -13,8 +13,11 @@ commands =
     coverage report -m
 
 [testenv:cover]
+# TODO(kfarr): remove once infra supports constraints for this target
+install_command = pip install -U {opts} {packages}
 deps =
-    {[testenv]deps}
+    -r{toxinidir}/requirements.txt
+    -r{toxinidir}/test-requirements.txt
     diff_cover
 commands =
     python setup.py testr --coverage --testr-args='{posargs}'
@@ -23,6 +26,8 @@ commands =
     diff-cover --fail-under 100 coverage.xml
 
 [testenv:releasenotes]
+# TODO(kfarr): remove once infra supports constraints for this target
+install_command = pip install -U {opts} {packages}
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:py34]
@@ -69,6 +74,8 @@ commands =
   bandit -r barbican -x tests -n5
 
 [testenv:venv]
+# TODO(kfarr): remove once infra supports constraints for this target
+install_command = pip install -U {opts} {packages}
 commands = {posargs}
 
 [testenv:debug]
@@ -84,6 +91,8 @@ commands =
   flake8 barbican setup.py
 
 [testenv:docs]
+# TODO(kfarr): remove once infra supports constraints for this target
+install_command = pip install -U {opts} {packages}
 commands=
     rm -rf api-guide/build
     python setup.py build_sphinx
@@ -92,6 +101,8 @@ commands=
 [testenv:api-guide]
 # This environment is called from CI scripts to test and publish
 # the API Guide to developer.openstack.org.
+# TODO(kfarr): remove once infra supports constraints for this target
+install_command = pip install -U {opts} {packages}
 commands =
   sphinx-build -W -b html -d api-guide/build/doctrees api-guide/source api-guide/build/html