interfaces: make the `peer` mixin not a Protocol to fix Python 3.10 failures I can't find any documentation on this, but it appears that Protocol class attributes don't get inherited in subclasses that explicitly subclass a Protocol until Python 3.11, which caused a ton of failures in CI on macOS and Windows (which both test using Python 3.9). The problem started with 1df97507c6b8, and typically manifested as most tests failing to access `ui` on various `peer` classes. Here's a short proof of concept: from __future__ import annotations from typing import ( Protocol, ) class peer(Protocol): limitedarguments: bool = False def __init__(self, arg1, arg2, remotehidden: bool = False) -> None: self.arg1 = arg1 self.arg2 = arg2 class subclass(peer): def __init__(self, arg1, arg2): super(subclass, self).__init__(arg1, arg2, False) sub = subclass(1, 2) print("sub.arg1 is %r" % sub.arg1) When run with Python 3.8.10, 3.9.13, and 3.10.11, the result is: $ py -3.8 prot-test.py Traceback (most recent call last): File "prot-test.py", line 20, in <module> print("sub.arg1 is %r" % sub.arg1) AttributeError: 'subclass' object has no attribute 'arg1' On Python 3.11.9, 3.12.7, and 3.13.0, the result is: $ py -3.11 ../prot-test.py sub.arg1 is 1 Explicitly adding annotations to `peer` like `limitedarguments` didn't help.