sys.settrace causes AttributeError during ssl import

[timofej673]

Bug report

Bug description:

When using a simple trace function, importing ssl fails with an AttributeError.
The same import works normally without sys.settrace().
Tested on:
Python 3.16.0a0 (heads/main:24e5a55ccb0, Aug 28 2026, 02:25:05) [MSC v.1951 64 bit (AMD64)] on win32
Python 3.14.5 (tags/v3.14.5:5607950, May 10 2026, 10:43:50) [MSC v.1944 64 bit (AMD64)] on win32
Python 3.13.14 (tags/v3.13.14:fd17997, Jun 10 2026, 13:03:48) [MSC v.1944 64 bit (AMD64)] on win32

import sys
def trace(*args):
    a = print
    a(args)
    return a

sys.settrace(trace)
import ssl

Traceback:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    import ssl
  File "D:\my\pythons\cpython\Lib\ssl.py", line 415, in <module>
    class Purpose(_ASN1Object, _Enum):
    ...<3 lines>...
        CLIENT_AUTH = '1.3.6.1.5.5.7.3.2'
  File "D:\my\pythons\cpython\Lib\enum.py", line 574, in __new__
    enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
  File "D:\my\pythons\cpython\Lib\enum.py", line 257, in __set_name__
    enum_member = enum_class._new_member_(enum_class, *args)
  File "D:\my\pythons\cpython\Lib\ssl.py", line 400, in __new__
    return super().__new__(cls, *_txt2obj(oid, name=False))
           ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<string>", line 1, in <lambda>
  File "D:\my\pythons\cpython\Lib\enum.py", line 1296, in __str__
    return "%s.%s" % (self.__class__.__name__, self._name_, )
                                               ^^^^^^^^^^^
AttributeError: 'Purpose' object has no attribute '_name_'. Did you mean '.name' instead of '._name_'?

CPython versions tested on:

CPython main branch, 3.14, 3.13

Operating systems tested on:

Windows

[StanFromIreland]

This isn't a bug. It's because your trace function returns print as the local trace function, so Python calls print(frame, 'return', arg) which stringifies arg. ssl.Purpose mixes in a namedtuple, so its __new__'s return event fires inside enum._proto_member.__set_name__, before _name_ is assigned so Enum.__str__ raises AttributeError. Similarly, this can be reproduced with:

import sys
class C:
    def __new__(cls, x): return super().__new__(cls)
    def __init__(self, x): self.x = x
    def __str__(self): return self.x

sys.settrace(lambda *a: print)
C(1)