Course Overview migrations fix: Readd the Facebook URL field.

openedx/core/djangoapps/content/course_overviews/migrations/0009_readd_facebook_url.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('course_overviews', '0008_remove_courseoverview_facebook_url'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='courseoverview',
+            name='facebook_url',
+            field=models.TextField(null=True),
+        ),
+    ]