Added contrib.auth migration for refs #13147.

django/contrib/auth/migrations/0004_alter_user_username_opts.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+import django.core.validators
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('auth', '0003_alter_user_email_max_length'),
+    ]
+
+    # No database changes; modifies validators and error_messages (#13147).
+    operations = [
+        migrations.AlterField(
+            model_name='user',
+            name='username',
+            field=models.CharField(error_messages={'unique': 'A user with that username already exists.'}, max_length=30, validators=[django.core.validators.RegexValidator('^[\\w.@+-]+$', 'Enter a valid username. This value may contain only letters, numbers and @/./+/-/_ characters.', 'invalid')], help_text='Required. 30 characters or fewer. Letters, digits and @/./+/-/_ only.', unique=True, verbose_name='username'),
+        ),
+    ]