Sometimes there is nothing, sometimes lines are duplicated.
Duplicated lines problem appears, because Python root logger
handler and Flask's `werkzeug` logger handler both write the
same message. `cheat.sh` is hit, because it sets this root
logging handler.
Normally `werkzeug` doesn't setup its own handler if it sees
that there are some handlers that process its messages. This
in case of `cheat.sh` resulted in no stderr logging at all.
No Exceptions either. Because `werkzeug` catches the
exceptions and logs them.
Hovewer, sometimes `werkzeug` starts too early, befora app
is imported (https://github.com/pallets/werkzeug/issues/1969)
and sets its logger anyway, before the app itself, resulting
in duplicating lines. In that case app root handler needs to
skip lines from `werkzeug`.
Kudos to @brandon-rhodes for `logging_tree` awesomeness
Anatoli Babenia