Fix TestDefaultTZDateTimeField

Author: blueyed

tests/test_fields.py

@@ -1343,15 +1343,22 @@ def setup_class(cls):
         cls.field = serializers.DateTimeField()
         cls.kolkata = pytz.timezone('Asia/Kolkata')
 
+    @staticmethod
+    def is_utc(tz):
+        """Django 2.1 uses datetime.timezone.utc
+
+        Ref: https://github.com/django/django/pull/9484#issuecomment-399169042"""
+        return tz.utcoffset(None).total_seconds() == 0.0
+
     def test_default_timezone(self):
-        assert self.field.default_timezone() == utc
+        assert self.is_utc(self.field.default_timezone())
 
     def test_current_timezone(self):
-        assert self.field.default_timezone() == utc
+        assert self.is_utc(self.field.default_timezone())
         activate(self.kolkata)
         assert self.field.default_timezone() == self.kolkata
         deactivate()
-        assert self.field.default_timezone() == utc
+        assert self.is_utc(self.field.default_timezone())
 
 
 @pytest.mark.skipif(pytz is None, reason='pytz not installed')