Extra data is a field in Django that will disappear sooner or later, …

…so this field is not required anymore when creating a new Statement/responds manually in Django Admin.

chatterbot/ext/django_chatterbot/migrations/0011_blank_extra_data.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.4 on 2017-08-20 13:55
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_chatterbot', '0010_statement_text'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='statement',
+            name='extra_data',
+            field=models.CharField(blank=True, max_length=500),
+        ),
+    ]