Update constraints support

Add library special-casing now that instack_undercloud is part of the global requirements.
Inspired by I68732c10e3f0dc4770b8639989cb24e264110d37.

Change-Id: I63919761fca37d3b3b6a615fba3bf99cf1fd4dac
Closes-Bug: #1699543

tox.ini

@@ -1,12 +1,18 @@
 [tox]
-minversion = 1.6
+minversion = 2.0
 skipsdist = True
 envlist = py35,py27,pep8
 
 [testenv]
 usedevelop = True
-install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
-setenv = VIRTUAL_ENV={envdir}
+install_command = {toxinidir}/tools/tox_install.sh {env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
+setenv =
+   VIRTUAL_ENV={envdir}
+   BRANCH_NAME=master
+   CLIENT_NAME=instack-undercloud
+   LANG=en_US.UTF-8
+   LANGUAGE=en_US:en
+   LC_ALL=C
 deps = -r{toxinidir}/test-requirements.txt
        -r{toxinidir}/requirements.txt
 commands = python setup.py testr --slowest --testr-args='{posargs}'
@@ -27,7 +33,9 @@ commands =
     flake8
     bash -c "find scripts -type f | xargs bashate -v -iE006"
     dib-lint
-setenv = ELEMENTS_DIR=elements
+setenv =
+   {[testenv]setenv}
+   ELEMENTS_DIR=elements
 
 [testenv:cover]
 commands = python setup.py test --coverage --coverage-package-name=instack_undercloud --testr-args='{posargs}'