Using os-testr to get better report

As a wrapper of testr, os-testr uses subunit-trace
for output and builds some helpful extra
functionality around testr

Reference link:
http://docs.openstack.org/developer/os-testr/index.html

Change-Id: I5eb1ea062334c06f5e95ef54367e427b98a17bac

test-requirements.txt

@@ -25,6 +25,7 @@ testresources>=0.2.4 # Apache-2.0/BSD
 reno>=1.8.0 # Apache-2.0
 # Next are used in integration tests only
 os-collect-config # Apache-2.0
+os-testr>=0.8.0 # Apache-2.0
 paramiko>=2.0 # LGPLv2.1+
 tempest>=14.0.0 # Apache-2.0
 gabbi>=1.26.1 # Apache-2.0

tox.ini

@@ -13,7 +13,7 @@ deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =
   find {toxinidir} -not -path '{toxinidir}/.tox/*' -name '*.py[c|o]' -delete
-  python setup.py testr --slowest --testr-args='{posargs}'
+  ostestr --slowest '{posargs}'
 
 whitelist_externals =
   bash