From 4a94c14c50ce6150cf9b29395c592d43f79ed569 Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Mon, 2 Jan 2017 22:22:22 -0500
Subject: [PATCH 1/2] Add test capturing known limitation on add_metaclass. Ref
 #127.

---
 test_six.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/test_six.py b/test_six.py
index b8543a93e..c4a9ebe9c 100644
--- a/test_six.py
+++ b/test_six.py
@@ -833,6 +833,30 @@ class MySlotsWeakref(object):
     assert type(MySlotsWeakref) is Meta
 
 
+def test_add_metaclass_child_meta():
+    """
+    Capture the known failure in the rare case where the parent
+    has a metaclass that is a superclass of the metaclass used
+    with the decorator (#127).
+    """
+    class MetaA(type): pass
+    class MetaB(type): pass
+
+    class A(object): pass
+    A = six.add_metaclass(MetaA)(A)
+
+    class B(object): pass
+    B = six.add_metaclass(MetaB)(B)
+
+    class MetaC(MetaA, MetaB): pass
+
+    with py.test.raises(TypeError) as exc:
+        class C(A, B): pass
+        C = six.add_metaclass(MetaC)(C)
+
+    assert 'metaclass conflict' in str(exc.value)
+
+
 @py.test.mark.skipif("sys.version_info[:2] < (2, 7) or sys.version_info[:2] in ((3, 0), (3, 1))")
 def test_assertCountEqual():
     class TestAssertCountEqual(unittest.TestCase):

From 85b52133a5e77d0fdb142b9fc3605368a1c43387 Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Mon, 2 Jan 2017 22:27:03 -0500
Subject: [PATCH 2/2] Update documentation to capture the caveat about suitable
 usage. Ref #127.

---
 documentation/index.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/documentation/index.rst b/documentation/index.rst
index 30374519a..bde2c8731 100644
--- a/documentation/index.rst
+++ b/documentation/index.rst
@@ -356,6 +356,12 @@ Python 2 and 3.
            pass
        MyClass = add_metaclass(Meta)(MyClass)
 
+   This technique works by re-building MyClass from the indicated metaclass,
+   but in the rare case where the parent has a metaclass that is a
+   superclass of the metaclass used with the decorator, this approach will
+   fail with a TypeError. See `issue 127
+   <https://github.com/benjaminp/six/issues/127>`_ for details.
+
 
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