t`.

            There are situations where prompt_toolkit applications are created
            in one thread, but will later run in a different thread (Ptpython
            is one example. The REPL runs in a separate thread, in order to
            prevent interfering with a potential different event loop in the
            main thread. The REPL UI however is still created in the main
            thread.) We could decide to not support creating prompt_toolkit
            objects in one thread and running the application in a different
            thread, but history loading is the only place where it matters, and
            this solves it.
        NrC