Jinja2 raise extension

Extend Jinja2 envrionment with a raise method so that
we can add logic in Jinja2 and raise errors.

In jinja2 template the raise method can be used like this:

 {%- if condition %}
   {{ raise('MESSAGE') }}
 {%- endif %}

Change-Id: Idaa1d570b129aa6c8c117b8087d1aad7ae987a47

releasenotes/notes/jinja2-template-render-raise-extension-87c7ed150a252ff5.yaml

@@ -0,0 +1,12 @@
+---
+other:
+  - |
+    The jinja2 template rendering function is extensended with a ``raise``
+    method. This can be used to raise errors conditionally in the Jinja2
+    templated tripleo-heat-tempaltes, for example in case some required property
+    is not defined in roles_data or network_data. The following example
+    demonstrates how to raise an error conditionally in a template::
+
+      {%- if condition %}
+        {{ raise('MESSAGE') }}
+      {%- endif %}

tripleo_common/tests/utils/test_template.py

@@ -37,6 +37,11 @@ JINJA_SNIPPET = r"""
       DefaultPasswords: {get_attr: [DefaultPasswords, passwords]}
 {% endfor %}"""
 
+JINJA_RAISE_CONFIG = r"""
+# Jinja raise extension
+{{ raise('MESSAGE') }}
+"""
+
 ROLE_DATA_YAML = r"""
 -
   name: CustomRole
@@ -390,6 +395,20 @@ class ProcessTemplatesTest(base.TestCase):
         self.assertTrue(
             {'name': []} == template_utils.get_j2_excludes_file(swift))
 
+    def test_j2_render_and_put_raise_in_template(self):
+
+        # setup swift
+        swift = mock.MagicMock()
+        swift.get_object = mock.MagicMock()
+        swift.get_container = mock.MagicMock()
+
+        # Test
+        args = (swift, JINJA_RAISE_CONFIG, {'role': 'CustomRole'},
+                'customrole-config.yaml', constants.DEFAULT_CONTAINER_NAME)
+        self.assertRaises(RuntimeError,
+                          template_utils.j2_render_and_put,
+                          *args)
+
     def test_heat_resource_exists(self):
         heat_client = mock.MagicMock()
         stack = mock.MagicMock(stack_name='overcloud')

tripleo_common/utils/template.py

@@ -64,14 +64,18 @@ class J2SwiftLoader(jinja2.BaseLoader):
 def j2_render_and_put(swift, j2_template, j2_data, yaml_f,
                       container=constants.DEFAULT_CONTAINER_NAME):
 
+    def raise_helper(msg):
+        raise jinja2.exceptions.TemplateError(msg)
+
     # Search for templates relative to the current template path first
     template_base = os.path.dirname(yaml_f)
     j2_loader = J2SwiftLoader(swift, container, template_base)
 
     try:
         # Render the j2 template
-        template = jinja2.Environment(loader=j2_loader).from_string(
-            j2_template)
+        jinja2_env = jinja2.Environment(loader=j2_loader)
+        jinja2_env.globals['raise'] = raise_helper
+        template = jinja2_env.from_string(j2_template)
         r_template = template.render(**j2_data)
     except jinja2.exceptions.TemplateError as ex:
         error_msg = ("Error rendering template %s : %s"