Add a migration that was generated for Django 2.

common/djangoapps/third_party_auth/migrations/0026_auto_20200401_1932.py

@@ -0,0 +1,20 @@
+# Generated by Django 2.0.13 on 2020-04-01 19:32
+
+from django.db import migrations, models
+import django.db.models.deletion
+import third_party_auth.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('third_party_auth', '0025_auto_20200303_1448'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='samlproviderconfig',
+            name='saml_configuration',
+            field=models.ForeignKey(blank=True, limit_choices_to=third_party_auth.models.active_saml_configurations_filter, null=True, on_delete=django.db.models.deletion.SET_NULL, to='third_party_auth.SAMLConfiguration'),
+        ),
+    ]