Enable tox to run unit tests

Change-Id: I5517be776cd240133c8f8aee0863c80a567d0591
Partially-Implements: tox-testcases

.testr.conf

@@ -0,0 +1,7 @@
+[DEFAULT]
+test_command=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
+             OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
+             OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-60} \
+             ${PYTHON:-python} -m subunit.run discover -t ./ ${OS_TEST_PATH:-./valence/tests/unit} $LISTOPT $IDOPTION
+test_id_option=--load-list $IDFILE
+test_list_option=--list

tox.ini

@@ -11,7 +11,7 @@ install_command =
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt
-commands = python setup.py test --slowest --testr-args='{posargs}'
+commands = python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:common-constraints]
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}