Disable pyXY tests on internal CI

this repo has no actual unit tests and when executing test runner
attempts to run actual tempest tests.

The CI job checks the list of default envs before runnning given
tox env. While this is actually wrong (those pyXY envs are
actually auto-generated by tox), removing them from default env
list unblocks our internal CI.

Change-Id: I83701f70249d9151b1e88c96713411f0366e46b3
diff --git a/tox.ini b/tox.ini
index 7b8aeec..798be25 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py35,pep8
+envlist = pep8
 minversion = 0.1
 skipsdist = True