**Bug report** In acf7403f9baea3ae1119fc6b4a3298522188bf96 (#30582), @ethanfurman changed the "Invalid enum member name" error message to "invalid enum member name(s)": https://github.com/python/cpython/blob/b2694ab46997746eae7e913738623b39f6334473/Lib/enum.py#L482-L484 (This was later reverted in 42a64c03ec5c443f2a5c2ee4284622f5d1f5326c and reintroduced in 83d544b9292870eb44f6fca37df0aa351c4ef83a, but I believe the code to be the same). However, the commit also removed `{0}` from the format string, thus removing the invalid names from the error messages. As a result, the error message is now less descriptive: ```pytb $ python3.10 -c "import enum; enum.Enum('A', ['mro'])" Traceback (most recent call last): File "<string>", line 1, in <module> File "/usr/lib/python3.10/enum.py", line 387, in __call__ return cls._create_( File "/usr/lib/python3.10/enum.py", line 518, in _create_ enum_class = metacls.__new__(metacls, class_name, bases, classdict) File "/usr/lib/python3.10/enum.py", line 208, in __new__ raise ValueError('Invalid enum member name: {0}'.format( ValueError: Invalid enum member name: mro ``` ```pytb $ python3.11 -c "import enum; enum.Enum('A', ['mro'])" Traceback (most recent call last): File "<string>", line 1, in <module> File "/usr/lib/python3.11/enum.py", line 791, in __call__ return cls._create_( ^^^^^^^^^^^^^ File "/usr/lib/python3.11/enum.py", line 966, in _create_ return metacls.__new__(metacls, class_name, bases, classdict, boundary=boundary) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/enum.py", line 483, in __new__ raise ValueError('invalid enum member name(s) '.format( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ValueError: invalid enum member name(s) ``` Given that the `.format()` is still there, I'm assuming that was an accident. (Found by running `flake8` over `Lib/` out of curiosity, see https://github.com/python/cpython/issues/93010#issuecomment-1133402591) **Your environment** - CPython versions tested on: Python 3.11.0b1 - Operating system and architecture: Archlinux x86_64