[Bugfix] 修改初始化一些节点时，assets_node表不存在的问题

apps/assets/apps.py

 from __future__ import unicode_literals
 
 from django.apps import AppConfig
+from django.db.models.signals import post_migrate
+
+
+def initial_some_nodes():
+    from .models import Node
+    Node.initial_some_nodes()
+
+
+def initial_some_nodes_callback(sender, **kwargs):
+    initial_some_nodes()
 
 
 class AssetsConfig(AppConfig):
@@ -9,5 +19,7 @@ class AssetsConfig(AppConfig):
     def ready(self):
         super().ready()
         from . import signals_handler
-        from .models import Node
-        Node.initial_some_nodes()
+        try:
+            initial_some_nodes()
+        except Exception:
+            post_migrate.connect(initial_some_nodes_callback, sender=self)