Merge pep8 and bandit into linters

Create new linters environment consisting of pep8 and bandit.
Keep pep8 as an alias for linters and add a message when invoked.

Once this change is in, the infra job can be changed to only run
linters job, this allows to run one less job for each change.

Change-Id: Ib15be94491232d63a345d6fc19869095a2537310

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 minversion = 1.6
 skipsdist = True
-envlist = py34,py27,pep8,bandit,releasenotes
+envlist = py34,py27,linters,releasenotes
 
 [testenv]
 usedevelop = True
@@ -16,9 +16,17 @@ commands = find . -type f -name "*.pyc" -delete
            python setup.py testr --slowest --testr-args='{posargs}'
 whitelist_externals = find
 
-[testenv:pep8]
+[testenv:linters]
 commands =
   flake8
+  bandit -c bandit.yaml -r keystoneclient -n5 -p keystone_conservative
+
+[testenv:pep8]
+whitelist_externals =
+  echo
+commands =
+  {[testenv:linters]commands}
+  echo "Use tox -e linters instead"
 
 [testenv:venv]
 commands = {posargs}