Change tox file

Add upper-constraints and min tox version.

This will prevent taking in packages that
are greater then what is defined in the
upper-constraints

Change-Id: Id557b9c47abf275de83516ccecd2d1b3eb0cfdd5

tox.ini

@@ -1,20 +1,21 @@
 [tox]
 envlist = py27,pep8
-minversion = 1.6
+minversion = 2.0
 skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command  = pip install -U {opts} {packages}
+install_command =
+    pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 setenv =
     VIRTUAL_ENV={envdir}
     DISCOVER_DIRECTORY=tests
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-       psutil==3.0.1
 whitelist_externals = bash
                       find
 commands =
+  pip install psutil==3.0.1
   find . -type f -name "*.pyc" -delete
   nosetests -w tests/ -e tests_to_fix