Perform oslo-incubator code sync.

run_tests.sh cannot install a virtualenv with tools/install_venv.py as
tools/install_venv_common.py depends on oslo.config which is an external
dependency. The virtualenv installer should not depend on any external
dependencies. Fix this by performing a code sync with oslo-incubator.

Note this adds a new dependency on six and changes the way versioning is
determined.

Change-Id: Ifb67bbfeec4eabc943c2a88a34fe535c57f174a1
Use testr instead of nose.

Part of blueprint grizzly-testtools

Change-Id: I76dee19781eaac21901b5c0258e83a42180c1702
Merge "Perform oslo-incubator code sync."
Merge "Use testr instead of nose."