Decorator which executes callback if wrapped Fabric task fails.

gistfile1.py

def on_fail(func):
    """ Return decorator which executes callback if wrapped tasks failes.

    Usage:
        def log_failure():
            print('Some failure.')

        @task
        @on_fail(log_failure):
        def git_fetch():
            abort('Failure!')


    :param func: A callable that is executed on failure of wrapped task.
    :return: A decorator.

    """
    def decorator(t):
        @wraps(t)
        def wrapper(*args, **kwargs):
            try:
                # warn_only must be False, so Fabric raises a SystemExit when
                # tasks failes.
                with settings(warn_only=False):
                    return t(*args, **kwargs)
            except SystemExit:
                print('Task \'%s\' failed!' % t.func_name)
                func()

        return wrapper
    return decorator