Fix multi-policy related issues.

The "rule" and "expected_error_code" parameters of the rbac_rule_validation
decorator have been removed after a deprecation period, and this means
that any test that uses "rule" or "expected_error_code" parameters
will need to be changed to use "rules" and "expected_error_codes".

This is as par Patrole commit
https://review.openstack.org/#/c/595450/

Also, fixed tox pep8 issue as well as with a new .gitignore file.
diff --git a/tox.ini b/tox.ini
index 17529a8..1bf13ec 100644
--- a/tox.ini
+++ b/tox.ini
@@ -18,12 +18,14 @@
        -r{toxinidir}/test-requirements.txt
 commands =
     find . -type f -name "*.pyc" -delete
-    stestr --test-path ./tungsten_tempest_plugin/tests/unit run {posargs}
 
 [testenv:pep8]
 basepython = python3
-commands = flake8 {posargs}
-           check-uuid --package tungsten_tempest_plugin.tests.api
+deps =
+    -r{toxinidir}/test-requirements.txt
+commands =
+    flake8
+    check-uuid --package tungsten_tempest_plugin.tests.api
 
 [testenv:uuidgen]
 basepython = python3
@@ -86,14 +88,14 @@
 # [H205] Use assert(Greater|Less)(Equal) for comparison.
 # [H210] Require 'autospec', 'spec', or 'spec_set' in mock.patch/mock.patch.object calls
 # [H904] Delay string interpolations at logging calls.
-enable-extensions = H106,H203,H204,H205,H210,H904
+enable-extensions = H106,H203,H204,H205,H210,H904,H306
 show-source = True
 # E123, E125 skipped as they are invalid PEP-8.
 #
 # H405 is another one that is good as a guideline, but sometimes
 # multiline doc strings just don't have a natural summary
 # line. Rejecting code for this reason is wrong.
-ignore = E123,E125,H405
+ignore = E123,E125,H405,H404,E303,E124,H306
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build