Make pep8 *the* linting interface

According to the PTI (=Python Test Interface,
http://governance.openstack.org/reference/cti/python_cti.html), pep8
is the interface for codestyle checks. Move all tests from linters to
pep8.

This basically reverts Ic9efdcb13978d2f29312a4a1f0fdd859d55c8398.

Depends-On: I9346e4bf8c3a50de088c6a157f0d871c0a9333a1
Change-Id: I99df6de57d345c40e39801d66575d35d0d8a36a9

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 minversion = 1.6
 skipsdist = True
-envlist = py34,py27,linters,docs,genconfig,releasenotes
+envlist = py34,py27,pep8,docs,genconfig,releasenotes
 
 [testenv]
 usedevelop = True
@@ -82,13 +82,13 @@ commands =
   nosetests -v \
       keystone/tests/unit/backend/legacy_drivers/resource/V8/sql.py
 
-[testenv:linters]
+[testenv:pep8]
 deps =
      .[bandit]
      {[testenv]deps}
 commands =
   flake8
-  # Run bash8 during linters runs to ensure violations are caught by
+  # Run bash8 during pep8 runs to ensure violations are caught by
   # the check and gate queues
   bashate examples/pki/gen_pki.sh
   # Check that .po and .pot files are valid.
@@ -97,16 +97,6 @@ commands =
   # Run security linter
   bandit -c bandit.yaml -r keystone -n5 -p gate
 
-[testenv:pep8]
-# Previous name of linters target, kept for compatibility. The infra jobs
-# will run the linters job.
-deps = {[testenv:linters]deps}
-whitelist_externals =
-  {[testenv]whitelist_externals}
-  echo
-commands = {[testenv:linters]commands}
-           echo "Use tox -e linters instead"
-
 [testenv:cover]
 commands = python setup.py testr --coverage --testr-args='{posargs}'