class retry(object):
    """A retry decorator."""

    def __init__(self,
                 exception=Exception,
                 timeout=None,
                 retries=None,
                 interval=0.001,
                 logfun=lambda s: print(s, file=sys.stderr),
                 ):
        if timeout and retries:
            raise ValueError("timeout and retries args are mutually exclusive")
        self.exception = exception
        self.timeout = timeout
        self.retries = retries
        self.interval = interval
        self.logfun = logfun

    def __iter__(self):
        if self.timeout:
            stop_at = time.time() + self.timeout
            while time.time() < stop_at:
                yield
        elif self.retries:
            for _ in range(self.retries):
                yield
        else:
            while True:
                yield

    def sleep(self):
        if self.interval is not None:
            time.sleep(self.interval)

    def __call__(self, fun):
        @functools.wraps(fun)
        def wrapper(*args, **kwargs):
            exc = None
            for _ in self:
                try:
                    return fun(*args, **kwargs)
                except self.exception as _:
                    exc = _
                    if self.logfun is not None:
                        self.logfun(exc)
                    self.sleep()
                    continue
            if PY3:
                raise exc
            else:
                raise

        # This way the user of the decorated function can change config
        # parameters.
        wrapper.decorator = self
        return wrapper

def retry_before_failing(retries=NO_RETRIES):
    """Decorator which runs a test function and retries N times before
    actually failing.
    """
    return retry(exception=AssertionError, timeout=None, retries=retries)

@retry_before_failing()
def test():
　　pass