fix flaky test: model_fields_.test_embedded_model.ModelTests.test_pre_save

Author: timgraham

tests/model_fields_/test_embedded_model.py

@@ -1,4 +1,5 @@
 import operator
+from datetime import timedelta
 
 from django.core.exceptions import FieldDoesNotExist, ValidationError
 from django.db import models
@@ -74,7 +75,9 @@ def test_pre_save(self):
         obj = Holder.objects.create(data=Data())
         auto_now = truncate_ms(obj.data.auto_now)
         auto_now_add = truncate_ms(obj.data.auto_now_add)
-        self.assertEqual(auto_now, auto_now_add)
+        # auto_now and auto_now_add may differ by a millisecond since they
+        # aren't generated simultaneously.
+        self.assertAlmostEqual(auto_now, auto_now_add, delta=timedelta(microseconds=1000))
         # save() updates auto_now but not auto_now_add.
         obj.save()
         self.assertEqual(truncate_ms(obj.data.auto_now_add), auto_now_add)