list_template_functions raises NotFound exception

Let list_template_functions raise NotFound exception instead,
while a nonexistent template version provided.

Change-Id: I1eff0f511abb0c1e098946e1d90b6bda9f59b249
Closes-Bug: #1505050

heat/engine/service.py

@@ -1172,7 +1172,12 @@ class EngineService(service.Service):
 
     def list_template_functions(self, cnxt, template_version):
         mgr = templatem._get_template_extension_manager()
-        tmpl_class = mgr[template_version]
+        try:
+            tmpl_class = mgr[template_version]
+        except KeyError:
+            raise exception.NotFound(_("Template with version %s not found") %
+                                     template_version)
+
         functions = []
         for func_name, func in six.iteritems(tmpl_class.plugin.functions):
             if func is not hot_functions.Removed:

heat/tests/test_engine_service.py

@@ -989,6 +989,21 @@ class StackServiceTest(common.HeatTestCase):
         self.assertEqual(sorted(expected, key=lambda k: k['functions']),
                          sorted(functions, key=lambda k: k['functions']))
 
+    @mock.patch('heat.engine.template._get_template_extension_manager')
+    def test_list_template_functions_version_not_found(self, templ_mock):
+        class DummyMgr(object):
+            def __getitem__(self, item):
+                raise KeyError()
+
+        templ_mock.return_value = DummyMgr()
+        version = 'dummytemplate'
+        ex = self.assertRaises(exception.NotFound,
+                               self.eng.list_template_functions,
+                               self.ctx,
+                               version)
+        msg = "Template with version %s not found" % version
+        self.assertEqual(msg, six.text_type(ex))
+
     def test_stack_list_all_empty(self):
         sl = self.eng.list_stacks(self.ctx)