Fix timezone warnings in models tests (#748)

Use timezone-aware datetimes.

Author: IvanAnishchuk

tests/test_models.py

@@ -1,5 +1,3 @@
-from datetime import datetime as dt
-
 import pytest
 from django.contrib.auth import get_user_model
 from django.core.exceptions import ImproperlyConfigured, ValidationError
@@ -305,23 +303,23 @@ def setUp(self):
         AccessToken.objects.create(
             id=1,
             token="555",
-            expires=dt.now(),
+            expires=timezone.now(),
             scope=2,
             application_id=3,
             user_id=1,
-            created=dt.now(),
-            updated=dt.now(),
+            created=timezone.now(),
+            updated=timezone.now(),
             source_refresh_token_id="0",
             )
         AccessToken.objects.create(
             id=2,
             token="666",
-            expires=dt.now(),
+            expires=timezone.now(),
             scope=2,
             application_id=3,
             user_id=1,
-            created=dt.now(),
-            updated=dt.now(),
+            created=timezone.now(),
+            updated=timezone.now(),
             source_refresh_token_id="1",
             )
 
@@ -340,9 +338,9 @@ def test_clear_expired_tokens_with_tokens(self):
         self.client.login(username="test_user", password="123456")
         oauth2_settings.REFRESH_TOKEN_EXPIRE_SECONDS = 0
         ttokens = AccessToken.objects.count()
-        expiredt = AccessToken.objects.filter(expires__lte=dt.now()).count()
+        expiredt = AccessToken.objects.filter(expires__lte=timezone.now()).count()
         assert ttokens == 2
         assert expiredt == 2
         clear_expired()
-        expiredt = AccessToken.objects.filter(expires__lte=dt.now()).count()
+        expiredt = AccessToken.objects.filter(expires__lte=timezone.now()).count()
         assert expiredt == 0