Use constraints for all the things

This configures tox to use upper-constraints for everything, except
environments used for post jobs (as constraints aren't supported there
yet).

Change-Id: I52530198b1970733cca6a3d0dedb42e416c69f54

tox.ini

@@ -3,6 +3,7 @@ envlist = py34,pep8,py27
 
 [testenv]
 usedevelop = True
+install_command = pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
@@ -12,6 +13,12 @@ commands =
     coverage report -m --fail-under 90
 
 [testenv:venv]
+# NOTE(amrith) The setting of the install_command in this location
+# is only required because currently infra does not actually
+# support constraints files for the docs job, and while
+# the environment variable UPPER_CONSTRAINTS_FILE is set, there's
+# no file there. It can be removed when infra changes this.
+install_command = pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 commands = {posargs}
 
 [testenv:pep8]
@@ -25,4 +32,4 @@ commands = python setup.py build_sphinx
 
 [flake8]
 max-complexity=15
-show-source = True
+show-source = True