flake8: Enable F811 (#4158)

third_party/3/waitress/proxy_headers.pyi

@@ -1,4 +1,4 @@
-from .utilities import BadRequest, logger, undquote
+from .utilities import BadRequest
 from collections import namedtuple
 from logging import Logger
 from typing import Any, Callable, Mapping, Sequence, Optional, Set

third_party/3/waitress/server.pyi

@@ -2,7 +2,6 @@ from . import wasyncore
 from .proxy_headers import proxy_headers_middleware
 from socket import SocketType
 from typing import Any, Sequence, Optional, Tuple, Union
-from waitress import trigger
 from waitress.adjustments import Adjustments
 from waitress.channel import HTTPChannel
 from waitress.compat import IPPROTO_IPV6, IPV6_V6ONLY

third_party/3/waitress/task.pyi

@@ -1,7 +1,7 @@
 from .buffers import ReadOnlyFileBasedBuffer
 from .channel import HTTPChannel
 from .compat import reraise, tobytes
-from .utilities import Error, build_http_date, logger, queue_logger
+from .utilities import Error
 from logging import Logger
 from threading import Condition, Lock
 from typing import Any, Deque, Mapping, Sequence, Optional, Set, Tuple