Change ugettext_lazy by gettext_lazy to remove django DeprecationWarning (#773)

Author: rhenter

oauth2_provider/models.py

@@ -8,7 +8,7 @@
 from django.db import models, transaction
 from django.urls import reverse
 from django.utils import timezone
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from .generators import generate_client_id, generate_client_secret
 from .scopes import get_scopes_backend

oauth2_provider/oauth2_validators.py

@@ -13,7 +13,7 @@
 from django.db.models import Q
 from django.utils import timezone
 from django.utils.timezone import make_aware
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 from oauthlib.oauth2 import RequestValidator
 
 from .exceptions import FatalClientError