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: I7ec32aefc9caac30f4e93704fc33b9a98cb1c622
Depends-On: https://review.openstack.org/555034
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

.zuul.yaml

@@ -117,7 +117,7 @@
         post-config:
           $OCTAVIA_CONF:
             DEFAULT:
-              debug: True
+              debug: true
             controller_worker:
               amphora_driver: amphora_noop_driver
               compute_driver: compute_noop_driver
@@ -224,6 +224,7 @@
         - osc-functional-devstack-tips:
             voting: false
         - neutron-grenade
+        - openstack-tox-lower-constraints
     gate:
       jobs:
         - build-openstack-sphinx-docs:
@@ -232,3 +233,4 @@
         - openstacksdk-functional-devstack
         - openstacksdk-functional-devstack-python3
         - neutron-grenade
+        - openstack-tox-lower-constraints

lower-constraints.txt

@@ -0,0 +1,37 @@
+appdirs==1.3.0
+coverage==4.0
+decorator==3.4.0
+deprecation==1.0
+dogpile.cache==0.6.2
+extras==1.0.0
+fixtures==3.0.0
+future==0.16.0
+iso8601==0.1.11
+jmespath==0.9.0
+jsonpatch==1.16
+jsonpointer==1.13
+jsonschema==2.6.0
+keystoneauth1==3.4.0
+linecache2==1.0.0
+mock==2.0.0
+mox3==0.20.0
+munch==2.1.0
+netifaces==0.10.4
+os-client-config==1.28.0
+os-service-types==1.2.0
+oslotest==3.2.0
+pbr==2.0.0
+python-mimeparse==1.6.0
+python-subunit==1.0.0
+PyYAML==3.12
+requests==2.14.2
+requests-mock==1.2.0
+requestsexceptions==1.2.0
+six==1.10.0
+stestr==1.0.0
+stevedore==1.20.0
+testrepository==0.0.18
+testscenarios==0.4
+testtools==2.2.0
+traceback2==1.4.0
+unittest2==1.1.0

tox.ini

@@ -101,3 +101,10 @@ exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 
 [doc8]
 extensions = .rst, .yaml
+
+[testenv:lower-constraints]
+basepython = python3
+deps =
+  -c{toxinidir}/lower-constraints.txt
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt