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: I54473d2fa682641f0a22beba344615807733016f
Depends-On: https://review.openstack.org/555034
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

.zuul.yaml

@@ -0,0 +1,7 @@
+- project:
+    check:
+      jobs:
+        - openstack-tox-lower-constraints
+    gate:
+      jobs:
+        - openstack-tox-lower-constraints

lower-constraints.txt

@@ -0,0 +1,73 @@
+alabaster==0.7.10
+appdirs==1.3.0
+Babel==2.3.4
+cliff==2.8.0
+cmd2==0.8.0
+coverage==4.0
+debtcollector==1.2.0
+decorator==3.4.0
+deprecation==1.0
+docutils==0.11
+dogpile.cache==0.6.2
+dulwich==0.15.0
+extras==1.0.0
+fixtures==3.0.0
+flake8==2.5.5
+hacking==0.12.0
+imagesize==0.7.1
+iso8601==0.1.11
+Jinja2==2.10
+jmespath==0.9.0
+jsonpatch==1.16
+jsonpointer==1.13
+keystoneauth1==3.2.0
+linecache2==1.0.0
+MarkupSafe==1.0
+mccabe==0.2.1
+mock==2.0.0
+monotonic==0.6
+msgpack-python==0.4.0
+munch==2.1.0
+netaddr==0.7.18
+netifaces==0.10.4
+openstacksdk==0.11.2
+os-client-config==1.28.0
+os-service-types==1.2.0
+osc-lib==1.7.0
+oslo.config==5.2.0
+oslo.context==2.19.2
+oslo.i18n==3.15.3
+oslo.log==3.30.0
+oslo.serialization==2.18.0
+oslo.utils==3.31.0
+oslosphinx==4.7.0
+pbr==2.0.0
+pep8==1.5.7
+prettytable==0.7.1
+pyflakes==0.8.1
+Pygments==2.2.0
+pyinotify==0.9.6
+pyparsing==2.1.0
+pyperclip==1.5.27
+python-dateutil==2.5.3
+python-mimeparse==1.6.0
+python-subunit==1.0.0
+pytz==2013.6
+PyYAML==3.12
+reno==2.5.0
+requests-mock==1.1.0
+requests==2.14.2
+requestsexceptions==1.2.0
+rfc3986==0.3.1
+simplejson==3.5.1
+six==1.9.0
+snowballstemmer==1.2.1
+Sphinx==1.6.2
+sphinxcontrib-websupport==1.0.1
+stevedore==1.20.0
+testrepository==0.0.18
+testscenarios==0.4
+testtools==1.4.0
+traceback2==1.4.0
+unittest2==1.1.0
+wrapt==1.7.0

tox.ini

@@ -58,3 +58,10 @@ exclude = .venv*,.tox,dist,*egg,build,.git,doc,*openstack/common*,*lib/python*,.
 
 [hacking]
 import_exceptions = six.moves,glareclient._i18n
+
+[testenv:lower-constraints]
+basepython = python3
+deps =
+  -c{toxinidir}/lower-constraints.txt
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt