add lower-constraints job

Create a tox environment for running the unit tests against the lower
bounds of the dependencies.

Create a lower-constraints.txt to be used to enforce the lower bounds
in those tests.

Add openstack-tox-lower-constraints job to the zuul configuration.

See http://lists.openstack.org/pipermail/openstack-dev/2018-March/128352.html
for more details.

Change-Id: I4a1b65911b7ee094dc3b654e0655a7e633c6819c
Depends-On: https://review.openstack.org/555034
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

.zuul.yaml

@@ -4,9 +4,11 @@
         - freezer-api-ubuntu-xenial
         - freezer-api-centos-7:
             voting: false
+        - openstack-tox-lower-constraints
     gate:
       jobs:
         - freezer-api-ubuntu-xenial
+        - openstack-tox-lower-constraints
     experimental:
       jobs:
         - freezer-api-opensuse-423

lower-constraints.txt

@@ -0,0 +1,87 @@
+alabaster==0.7.10
+alembic==0.9.8
+astroid==1.3.8
+Babel==2.5.3
+certifi==2018.1.18
+chardet==3.0.4
+coverage==4.5.1
+debtcollector==1.19.0
+decorator==4.2.1
+docutils==0.14
+dogpile.cache==0.6.5
+dulwich==0.19.0
+elasticsearch==2.4.1
+extras==1.0.0
+falcon==1.4.1
+fixtures==3.0.0
+flake8==2.5.5
+hacking==0.12.0
+idna==2.6
+imagesize==1.0.0
+iso8601==0.1.12
+Jinja2==2.10
+jsonschema==2.6.0
+keystoneauth1==3.4.0
+keystonemiddleware==4.21.0
+linecache2==1.0.0
+logilab-common==1.4.1
+Mako==1.0.7
+MarkupSafe==1.0
+mccabe==0.4.0
+mock==2.0.0
+monotonic==1.4
+msgpack==0.5.6
+netaddr==0.7.19
+netifaces==0.10.6
+openstackdocstheme==1.20.0
+os-api-ref==1.5.0
+oslo.cache==1.29.0
+oslo.config==5.2.0
+oslo.context==2.20.0
+oslo.db==4.35.0
+oslo.i18n==3.20.0
+oslo.log==3.37.0
+oslo.middleware==3.35.0
+oslo.policy==1.34.0
+oslo.serialization==2.25.0
+oslo.utils==3.36.0
+oslosphinx==4.18.0
+Paste==2.0.3
+PasteDeploy==1.5.2
+pbr==3.1.1
+pep8==1.7.1
+pycadf==2.7.0
+pyflakes==1.0.0
+Pygments==2.2.0
+pyinotify==0.9.6
+pylint==1.4.5
+pyparsing==2.2.0
+python-dateutil==2.7.0
+python-editor==1.0.3
+python-keystoneclient==3.15.0
+python-mimeparse==1.6.0
+python-subunit==1.2.0
+pytz==2018.3
+PyYAML==3.12
+reno==2.7.0
+requests==2.18.4
+rfc3986==1.1.0
+six==1.11.0
+snowballstemmer==1.2.1
+Sphinx==1.6.5
+sphinxcontrib-websupport==1.0.1
+SQLAlchemy==1.2.5
+sqlalchemy-migrate==0.11.0
+sqlparse==0.2.4
+statsd==3.2.2
+stevedore==1.28.0
+Tempita==0.5.2
+testrepository==0.0.20
+testresources==2.0.1
+testscenarios==0.5.0
+testtools==2.3.0
+traceback2==1.4.0
+unittest2==1.1.0
+urllib3==1.22
+WebOb==1.7.4
+wrapt==1.10.11

tox.ini

@@ -99,3 +99,10 @@ commands = sphinx-build -W -a -E -d releasenotes/build/doctrees -b html releasen
 
 [testenv:genpolicy]
 commands = oslopolicy-sample-generator --config-file etc/freezer/freezer-policy-generator.conf
+
+[testenv:lower-constraints]
+basepython = python3
+deps =
+  -c{toxinidir}/lower-constraints.txt
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt