Fix linter

(cherry picked from commit 92af870c)

aleksis/core/mixins.py

@@ -14,7 +14,7 @@ from django.db import models
 from django.db.models import JSONField, QuerySet
 from django.db.models.fields import CharField, TextField
 from django.forms.forms import BaseForm
-from django.forms.models import fields_for_model, ModelForm, ModelFormMetaclass
+from django.forms.models import ModelForm, ModelFormMetaclass, fields_for_model
 from django.http import HttpResponse
 from django.utils.functional import classproperty, lazy
 from django.utils.translation import gettext as _