Update authentication.py

Author: lnagel

rest_framework_sso/authentication.py

@@ -3,10 +3,7 @@
 
 import jwt.exceptions
 from django.utils.encoding import smart_str
-try:
-    from django.utils.translation import gettext_lazy as _
-except ImportError:
-    from django.utils.translation import ugettext as _
+from django.utils.translation import gettext_lazy as _
 from rest_framework import exceptions
 from rest_framework.authentication import BaseAuthentication, get_authorization_header