Fix lower-constraint deps handling

When the lower-constraints tox target was added, it was assumed the
install_command was just running the install and that the dependencies
and constraints were being set using "deps = ".

This fixed the install_command and deps to follow the expected pattern
so the lower-constraints job actual does install the lower constraints.

Raising libvirt-python minimum version as the existing version would
fail.

Change-Id: Icbbae373525dce3f13fcb38373d4c66160cf05d1
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

lower-constraints.txt

@@ -18,7 +18,7 @@ iso8601==0.1.11
 itsdangerous==0.24
 Jinja2==2.10
 keystoneauth1==3.4.0
-libvirt-python==3.5.0
+libvirt-python==3.7.0
 linecache2==1.0.0
 MarkupSafe==1.0
 mock==2.0.0

test-requirements.txt

@@ -6,7 +6,7 @@ hacking>=1.0.0,<1.2.0 # Apache-2.0
 
 coverage!=4.4,>=4.0 # Apache-2.0
 # used by libvirt driver
-libvirt-python!=4.1.0,>=3.5.0 # LGPLv2+
+libvirt-python!=4.1.0,>=3.7.0 # LGPLv2+
 python-subunit>=1.0.0 # Apache-2.0/BSD
 sphinx!=1.6.6,>=1.6.2 # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0

tox.ini

@@ -5,11 +5,12 @@ skipsdist = True
 
 [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}
+install_command = pip install {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning
 deps =
+    -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/requirements.txt
 commands = stestr run {posargs}