Added missing migration

backend/migrations/0007_auto_20150821_0818.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('backend', '0006_am_fd_comment'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='person',
+            name='username',
+            field=models.CharField(help_text='Debian SSO username', unique=True, max_length=255),
+            preserve_default=True,
+        ),
+    ]