[1.8.x] Fixed #26324 -- Fixed DurationField with fractional seconds on SQLite.

Backport of 4f0cd0fd162122da96978b357ac9fc9534529410 from master

django/db/models/fields/__init__.py

@@ -1680,7 +1680,8 @@ class DurationField(Field):
             return value
         if value is None:
             return None
-        return value.total_seconds() * 1000000
+        # Discard any fractional microseconds due to floating point arithmetic.
+        return int(round(value.total_seconds() * 1000000))
 
     def get_db_converters(self, connection):
         converters = []

docs/releases/1.8.12.txt

@@ -12,3 +12,6 @@ Bugfixes
 * Made ``MultiPartParser`` ignore filenames that normalize to an empty string
   to fix crash in ``MemoryFileUploadHandler`` on specially crafted user input
   (:ticket:`26325`).
+
+* Fixed data loss on SQLite where ``DurationField`` values with fractional
+  seconds could be saved as ``None`` (:ticket:`26324`).

tests/model_fields/test_durationfield.py

@@ -22,6 +22,12 @@ class TestSaveLoad(TestCase):
         loaded = NullDurationModel.objects.get()
         self.assertEqual(loaded.field, None)
 
+    def test_fractional_seconds(self):
+        value = datetime.timedelta(seconds=2.05)
+        d = DurationModel.objects.create(field=value)
+        d.refresh_from_db()
+        self.assertEqual(d.field, value)
+
 
 class TestQuerying(TestCase):