Drop python26 support for Kilo nova

Now that we have stopped running python26 jobs in the gate, remove
python26 from the list of jobs in tox

project-config patch: Ib495467e00e4b6abf2b3c2b9445b51652ba25167

Change-Id: I18262e91c9f5fc2381c6f5b37eb45b5f27aa81db
Use assertRaisesRegexp

Now that we don't support py26 we can use assertRaisesRegexp

Change-Id: If13527bc0f92891ca2afee4c260538ccf9074735
Use py27 version of assertRaisesRegexp

Now that we don't support py26 we can use the built in
assertRaisesRegexp (which takes slightly different parameters).

Change-Id: Icf30a75f353809984bafb202781120d16979f670
Merge "Drop python26 support for Kilo nova"
Merge "Use assertRaisesRegexp"
Merge "Use py27 version of assertRaisesRegexp"