Configures ruff as the one stop linter and resolves warnings it raised

src/documents/migrations/0001_initial.py

@@ -1,6 +1,4 @@
-# -*- coding: utf-8 -*-
 # Generated by Django 1.9 on 2015-12-20 19:10
-from __future__ import unicode_literals
 
 from django.db import migrations, models
 from django.conf import settings
@@ -32,7 +30,7 @@ class Migration(migrations.Migration):
                     models.TextField(
                         db_index=(
                             "mysql" not in settings.DATABASES["default"]["ENGINE"]
-                        )
+                        ),
                     ),
                 ),
                 ("created", models.DateTimeField(auto_now_add=True)),