EMNIST下载出现错误：
数据集下载链接：
url = 'http://www.itl.nist.gov/iaui/vip/cs_links/EMNIST/gzip.zip'
修改环境下的mnist.py文件：
/root/anaconda3/envs/PyTorch1.2/lib/python3.6/site-packages/torchvision/datasets/mnist.py
解决方案：
https://github.com/Tony-Y/pytorch_warmup/blob/master/examples/emnist/download.py
