Restore compatibility with PrettyTable < 0.7.2

PrettyTable 0.7.2 defaults to print a table even if
the resultset is empty. Restore previous behavior
to be in line with older prettytable releases.

Change-Id: Idd1d0c2c2f41966076517cbc8819ba9a5e097306
Added Conflict Exception to the exception code map

The Conflict Exception is added for HTTP error code 409.
However this exception is never raised as this class is not added to
the error_code map and always raises the ClientException whenever a
409 code is returned.

Fixes bug #1168826

Change-Id: I7045eae33533ff603f4aab61ea988264b46f0d09
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 "Restore compatibility with PrettyTable < 0.7.2"
Merge "Added Conflict Exception to the exception code map"
Merge "Perform oslo-incubator code sync."
Merge "Use testr instead of nose."