allow deprecation of a class with custom metaclass

scrapy/tests/test_utils_deprecate.py

@@ -177,3 +177,8 @@ class WarnWhenSubclassedTest(unittest.TestCase):
             Deprecated = create_deprecated_class('Deprecated', NewName, {'foo': 'bar'})
 
         self.assertEqual(Deprecated.foo, 'bar')
+
+    def test_deprecate_a_class_with_custom_metaclass(self):
+        Meta1 = type('Meta1', (type,), {})
+        New = Meta1('New', (), {})
+        Deprecated = create_deprecated_class('Deprecated', New)

scrapy/utils/deprecate.py

@@ -45,7 +45,7 @@ def create_deprecated_class(name, new_class, clsdict=None,
     OldName.
     """
 
-    class DeprecatedClass(type):
+    class DeprecatedClass(new_class.__class__):
 
         deprecated_class = None
         warned_on_subclass = False