small tox fixes

* remove py26: it no longer used in gates, and fails the tests on:

    (dt.datetime.now() - time_before).total_seconds(),
    AttributeError: 'datetime.timedelta' object has no
    attribute'total_seconds'`

* don't generate __pycache__ folders

Change-Id: Ifce1e77012bc3be7785597ab84b998209b866ae8

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py26,py27,py33,py34,pep8
+envlist = py27,py33,py34,pep8
 minversion = 1.6
 skipsdist = True
 
@@ -8,6 +8,7 @@ sitepackages = True
 usedevelop = True
 install_command = pip install -U --force-reinstall {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
+         PYTHONDONTWRITEBYTECODE = 1
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =