Store error info in execution result when failed

This makes sure that users are told executions failed due to something
is wrong in Qinling engine.

Change-Id: I19abb2ad4abe955bf18550bce04499d2c4f9bbb5
Story: 2002043
Task: 19687

qinling/engine/utils.py

@@ -151,4 +151,6 @@ def handle_execution_exception(execution_id, exc_str):
     LOG.error(
         'Error running execution %s: %s', execution_id, exc_str
     )
-    db_set_execution_status(execution_id, status.ERROR, '', {})
+    db_set_execution_status(
+        execution_id, status.ERROR, '', {'EngineError': exc_str}
+    )

qinling/tests/unit/engine/test_default_engine.py

@@ -324,7 +324,8 @@ class TestDefaultEngine(base.DbTestCase):
         execution = db_api.get_execution(execution_id)
         self.assertEqual(execution.status, status.ERROR)
         self.assertEqual(execution.logs, '')
-        self.assertEqual(execution.result, {})
+        self.assertEqual(execution.result,
+                         {'EngineError': 'Exception in prepare_execution'})
 
     @mock.patch('qinling.utils.etcd_util.get_service_url')
     def test_create_execution_package_type_function(
@@ -385,7 +386,8 @@ class TestDefaultEngine(base.DbTestCase):
 
         self.assertEqual(execution.status, status.ERROR)
         self.assertEqual(execution.logs, '')
-        self.assertEqual(execution.result, {})
+        self.assertEqual(execution.result,
+                         {'EngineError': 'Exception in scaleup_function'})
 
     @mock.patch('qinling.engine.utils.get_request_data')
     @mock.patch('qinling.engine.utils.url_request')