The following code worked in 3.8.5 but does not in 3.8.6 due to the fix for #39587:

```
import enum


class MyInt(int):
    def __new__(cls, value):
        return super().__new__(cls, value)

class HexMixin:
    def __repr__(self):
        return hex(self)

class MyIntEnum(HexMixin, MyInt, enum.Enum):
    pass


class Foo(MyIntEnum):
    TEST = 1

assert isinstance(Foo.TEST, MyInt)
assert repr(Foo.TEST) == "0x1"
```


In 3.8.6, the `Foo` enum itself fails to be created because `HexMixin` is now considered the member type instead of `MyInt`:

```
Traceback (most recent call last):
  File "enum_test.py", line 18, in <module>
    class Foo(MyIntEnum):
  File "/usr/local/Cellar/python@3.8/3.8.6/Frameworks/Python.framework/Versions/3.8/lib/python3.8/enum.py", line 215, in __new__
    enum_member = __new__(enum_class)
TypeError: object.__new__(Foo) is not safe, use int.__new__()
```

Actually, this is an issue with native types in general that define a 'tp_new' slot value ('!= NULL').

New changeset c266736ec1f9ebef38b134ceb4832df015711b38 by Ethan Furman in branch 'master':
bpo-41889: [Enum] fix multiple-inheritance regression (GH-22487)
https://github.com/python/cpython/commit/c266736ec1f9ebef38b134ceb4832df015711b38

New changeset 699e5e448919283578afe445069ab93b34bf8eae by Miss Islington (bot) in branch '3.8':
bpo-41889: [Enum] fix multiple-inheritance regression (GH-22487) (GH-23672)
https://github.com/python/cpython/commit/699e5e448919283578afe445069ab93b34bf8eae

New changeset be52ca45d9eb9c3e8941e46ddc67a210f0f4c6fa by Miss Islington (bot) in branch '3.9':
bpo-41889: [Enum] fix multiple-inheritance regression (GH-22487) (GH-23673)
https://github.com/python/cpython/commit/be52ca45d9eb9c3e8941e46ddc67a210f0f4c6fa