Explicitly name commands target environments

Naming envs like this is breaking the current
oslo periodic day job; a simple way to unbreak this
is to name them explicitly (which appears to be
more common).

So this changes the command listing to do just that
as well as lists py35 in the envlist (because its
a valid target).

Change-Id: I2a162604b60df8f18ff53069c6bf99cfecc4217e

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = py{34,27},functional,pep8,pip-missing-reqs
+envlist = py{35,34,27},functional,pep8,pip-missing-reqs
 skipsdist = True
 
 [testenv]
@@ -20,13 +20,25 @@ deps = -r{toxinidir}/test-requirements.txt
 # other way around. See: https://bugs.launchpad.net/testrepository/+bug/1212909
 commands =
   find . -type f -name "*.pyc" -delete
-  py27: bash tools/pretty_tox.sh '{posargs}'
-  py34: bash tools/pretty_tox3.sh '{posargs}'
-  py35: bash tools/pretty_tox3.sh '{posargs}'
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY OS_DEBUG GENERATE_HASHES
 # there is also secret magic in pretty_tox.sh which lets you run in a fail only
 # mode. To do this define the TRACE_FAILONLY environmental variable.
 
+[testenv:py27]
+commands =
+    {[testenv]commands}
+    bash tools/pretty_tox.sh '{posargs}'
+
+[testenv:py34]
+commands =
+    {[testenv]commands}
+    bash tools/pretty_tox3.sh '{posargs}'
+
+[testenv:py35]
+commands =
+    {[testenv]commands}
+    bash tools/pretty_tox3.sh '{posargs}'
+
 [testenv:pep8]
 basepython = python2.7
 deps = hacking