Accounts app improvements and tests

accounts/models.py

@@ -1,9 +1,7 @@
-from django.conf import settings
 from django.contrib.auth.models import User
 from django.core.validators import MinValueValidator
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
-
 from instances.models import Instance
 
 
@@ -11,6 +9,7 @@ class UserInstanceManager(models.Manager):
     def get_queryset(self):
         return super().get_queryset().select_related('instance', 'user')
 
+
 class UserInstance(models.Model):
     user = models.ForeignKey(User, on_delete=models.CASCADE)
     instance = models.ForeignKey(Instance, on_delete=models.CASCADE)