为User problems_status 添加默认值，并精简了相关代码

account/migrations/0003_auto_20150915_2025.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('account', '0002_user_problems_status'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='user',
+            name='problems_status',
+            field=models.TextField(default=b'{}'),
+        ),
+    ]