Use pretty_tox for running unit tests

Because it looks nicer, if nothing else.

Change-Id: I5bad21b84bcf0cc425aa200f7045f80f53d2d813

test-requirements.txt

@@ -17,3 +17,5 @@ testrepository>=0.0.18
 testtools>=0.9.36,!=1.2.0
 testscenarios>=0.4
 WebTest>=2.0
+# This is needed for subunit-trace
+tempest-lib>=0.1.0

tox.ini

@@ -13,7 +13,10 @@ install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 whitelist_externals = sh
-commands = python setup.py testr --slowest --testr-args='{posargs}'
+commands =
+  sh tools/pretty_tox.sh '{posargs}'
+# there is also secret magic in pretty_tox.sh which lets you run in a fail only
+# mode. To do this define the TRACE_FAILONLY environmental variable.
 
 [testenv:hashtest]
 # This is the same as default environment, but with a random PYTHONHASHSEED.