data problem

[Arrcil]

Extracting ./asset/data/mnist/train-images-idx3-ubyte.gz
Traceback (most recent call last):
File "train.py", line 75, in
data = tf.sg_data.Mnist(batch_size=batch_size)
File "/home/xujian/ac-gan-master/ac-gan-master/sugartensor/sg_data.py", line 40, in init
data_set = input_data.read_data_sets(Mnist._data_dir, reshape=reshape, one_hot=one_hot)
File "/home/xujian/.local/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/datasets/mnist.py", line 213, in read_data_sets
train_images = extract_images(f)
File "/home/xujian/.local/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/datasets/mnist.py", line 53, in extract_images
magic = _read32(bytestream)
File "/home/xujian/.local/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/datasets/mnist.py", line 35, in _read32
return numpy.frombuffer(bytestream.read(4), dtype=dt)[0]
File "/usr/lib/python2.7/gzip.py", line 268, in read
self._read(readsize)
File "/usr/lib/python2.7/gzip.py", line 303, in _read
self._read_gzip_header()
File "/usr/lib/python2.7/gzip.py", line 197, in _read_gzip_header
raise IOError, 'Not a gzipped file'
IOError: Not a gzipped file