Merge pull request apache#274 from airbnb/task_missing

Error message when task is gone on task details page

airflow/www/app.py

@@ -818,6 +818,12 @@ def task(self):
         dttm = dateutil.parser.parse(execution_date)
         form = DateTimeForm(data={'execution_date': dttm})
         dag = dagbag.get_dag(dag_id)
+        if not dag or task_id not in dag.task_ids:
+            flash(
+                "Task [{}.{}] doesn't seem to exist"
+                " at the moment".format(dag_id, task_id),
+                "error")
+            return redirect('/admin/')
         task = dag.get_task(task_id)
         task = copy.copy(task)
         task.resolve_template_files()
@@ -1096,7 +1102,7 @@ def graph(self):
         dag = dagbag.get_dag(dag_id)
         if dag_id not in dagbag.dags:
             flash('DAG "{0}" seems to be missing.'.format(dag_id), "error")
-            return redirect('/admin/dagmodel/')
+            return redirect('/admin/')
 
         root = request.args.get('root')
         if root: