Add json_parse and yaml_parse mistral expression functions

This change adds parsing of JSON and YAML as a mistral functions.

Change-Id: I9970abae47ca355861e37cdb5db0ab24d564b57a
Related-Bug: #1736707

setup.cfg

@@ -137,3 +137,6 @@ mistral.actions =
     tripleo.ansible-playbook = tripleo_common.actions.ansible:AnsiblePlaybookAction
     tripleo.templates.upload_default = tripleo_common.actions.templates:UploadTemplatesAction
     tripleo.plan.migrate = tripleo_common.actions.plan:MigratePlanAction
+mistral.expression.functions =
+    json_parse = tripleo_common.utils.mistral_expression_utils:json_parse_
+    yaml_parse = tripleo_common.utils.mistral_expression_utils:yaml_parse_

tripleo_common/utils/mistral_expression_utils.py

@@ -0,0 +1,24 @@
+#   Copyright 2015 Red Hat, Inc.
+#
+#   Licensed under the Apache License, Version 2.0 (the "License"); you may
+#   not use this file except in compliance with the License. You may obtain
+#   a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#   WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#   License for the specific language governing permissions and limitations
+#   under the License.
+
+from oslo_serialization import jsonutils
+import yaml
+
+
+def json_parse_(context, data):
+    return jsonutils.loads(data)
+
+
+def yaml_parse_(context, data):
+    return yaml.safe_load(data)