Stop trying to use a %s tox target

Tox appears to be very good at always installing the latest version of
itself when you use environment requirements. This was fine until latest
tox stopped accepting the %s environment (but only when you don't
specify the environment explicitly). This %s environment was added to
check that tox siblings behavior didn't interpolate strings, but we use
RawConfigParser now to prevent that and that shouldn't change any time
soon. Testing this otherwise seems painful.

Instead of simply deleting this test we modify it to use a new
acceptable name in order to test the running of a target with a non
default config file path.

Change-Id: Ie92f2a2536ea03ac2058659a083fb23151303ed0

test-playbooks/python/tox.ini

@@ -16,5 +16,5 @@ commands = sh -c "echo linters >> {posargs}"
 [testenv:non-default]
 commands = sh -c "echo non-default >> {posargs}"
 
-[testenv:%s]
+[testenv:foo]
 commands = sh -c "echo working"

test-playbooks/python/tox.yaml

@@ -76,12 +76,12 @@
           register: ALL_status
           failed_when: ALL_status is changed
 
-    - name: Run tox with tox_envlist = %s
+    - name: Run tox against a specific config file
       include_role:
         name: tox
       vars:
         # Make sure the tox_config_file option works
         tox_config_file: test-playbooks/python
-        tox_envlist: '%s'
+        tox_envlist: 'foo'
         # Make sure we test with verbose output even if the default changes
         tox_extra_args: '-vv'