Comment 2 for bug 1372250

Putting a breakpoint in at the installed oslo/db/__init__.py, sys.path:
['/home/robertc/work/openstack/oslo.db', '', '/home/robertc/work/openstack/oslo.db/.tox/py27/lib/python2.7', '/home/robertc/work/openstack/oslo.db/.tox/py27/lib/python2.7/plat-x86_64-linux-gnu', '/home/robertc/work/openstack/oslo.db/.tox/py27/lib/python2.7/lib-tk', '/home/robertc/work/openstack/oslo.db/.tox/py27/lib/python2.7/lib-old', '/home/robertc/work/openstack/oslo.db/.tox/py27/lib/python2.7/lib-dynload', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/home/robertc/work/openstack/oslo.db/.tox/py27/local/lib/python2.7/site-packages', '/home/robertc/work/openstack/oslo.db/.tox/py27/lib/python2.7/site-packages']

So the source tree is first on the python path, which means we should find things there first (as expected).