Flake8 F824 for global variable scoping

[cpswan]

Describe the bug

#355 introduced Flake8 7.2.0, which added a new variable scoping check. at_client currently fails that test throwing an F824 error:

./at_client/atclient.py:348:13: F824 `global should_be_running_lock` is unused: name is never assigned in scope
            global should_be_running_lock
            ^
./at_client/atclient.py:371:13: F824 `global should_be_running_lock` is unused: name is never assigned in scope
            global should_be_running_lock
            ^
./at_client/connections/atmonitorconnection.py:37:9: F824 `global should_be_running_lock` is unused: name is never assigned in scope
        global should_be_running_lock
        ^
./examples/repl.py:93:17: F824 `global shared_queue` is unused: name is never assigned in scope
                global shared_queue
                ^
4     F824 `global should_be_running_lock` is unused: name is never assigned in scope
4

d7f8394 put in place a workaround, and this ticket is to track its eventual removal.

Steps to reproduce

Run flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics --exclude .venv,.git without --ignore=F824

Expected behavior

Lints pass clean