Return a unique identifier for a given task.
    @param task: the XML element that represents a task
    @return a tuple with filename of task as first element

def get_task_id(task, base_path_or_url):
    """
    Return a unique identifier for a given task.
    @param task: the XML element that represents a task
    @return a tuple with filename of task as first element
    """
    name = task.get('name')
    if base_path_or_url:
        if Util.is_url(base_path_or_url):
            name = urllib.parse.urljoin(base_path_or_url, name)
        else:
            name = os.path.normpath(os.path.join(os.path.dirname(base_path_or_url), name))
    task_id = [name,
               task.get('properties'),
               task.get('runset'),
               ]
    return tuple(task_id)