Add yamllint check to lint job

Initial commit with bootstrapping non-voting configuration
for yamllint. Yamllint checks will be switched from 'warning'
to 'enabled' in subsequent commits together with code adjustments.

Also quotes %%%.* fields in netpol.yaml to make them valid.

Change-Id: I24cb0b7680f1fb9c0dfd98527e85440a6635d1d7

tox.ini

@@ -0,0 +1,21 @@
+[tox]
+minversion = 3.1
+envlist = docs
+skipsdist = True
+ignore_basepython_conflict = True
+
+[testenv]
+basepython = python3
+setenv = VIRTUAL_ENV={envdir}
+deps = -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+passenv = *_proxy *_PROXY
+
+[testenv:venv]
+commands = {posargs}
+
+[testenv:lint]
+deps = yamllint
+commands =
+  bash -c "yamllint -c {toxinidir}/yamllint.conf  */values* yamllint.conf"
+whitelist_externals =
+  bash

yamllint.conf

@@ -0,0 +1,49 @@
+---
+
+yaml-files:
+- '*.yaml'
+- '*.yml'
+- '.yamllint'
+
+rules:
+  braces:
+    level: warning
+  brackets:
+    level: warning
+  colons:
+    level: warning
+  commas:
+    level: warning
+  comments:
+    level: warning
+  comments-indentation:
+    level: warning
+  document-end:
+    level: warning
+  document-start:
+    level: warning
+  empty-lines:
+    level: warning
+  empty-values:
+    level: warning
+  hyphens:
+    level: warning
+  indentation:
+    spaces: 2
+    indent-sequences: whatever
+    level: warning
+  key-duplicates:
+    level: warning
+  key-ordering: disable
+  line-length: disable
+  new-line-at-end-of-file:
+    level: warning
+  new-lines:
+    level: warning
+  octal-values:
+    level: warning
+  quoted-strings: disable
+  trailing-spaces: enable
+  truthy:
+    level: warning
+...