Defective usage of ForecastExecutor.post_process()

The docstrings of AbstractExecutor.post_process() state that

    def post_process(self):
        """
        Execution post-processing

        Invoked after all children have finished executing but before the
        `finished` signal is emitted
        """
        pass

see also (https://gitlab.seismo.ethz.ch/indu/rt-ramsis/blob/529c548beae44c78dea1848f8ee45041db598a49/RAMSIS/core/tools/executor.py#L85-92).

Apparently this is not true. The post_process method of e.g. SerialExecutor is called every time the SerialExecutor._run_next method is executed (i.e. when the status of the child changed, too).

Child executors are asked to perform their main work in a separate thread. As a consequence, they return as soon as possible after being invoked. So even if implementing children using something like QThread within the executors run method the current design would fail.