Imports task dynamically given a module and a task name.

def load_task(module, task_name, params_str):
    """
    Imports task dynamically given a module and a task name.
    """
    if module is not None:
        __import__(module)
    task_cls = Register.get_task_cls(task_name)
    return task_cls.from_str_params(params_str)