Fix runtime exception

[healess]

Use this code. It is possible to train Imagenet.(tf v1.12) But there are some runtime exception so I fixed it. (It is also enrolled on issue https://github.com/MG2033/ShuffleNet/issues/5 https://github.com/MG2033/ShuffleNet/issues/11)

    except KeyboardInterrupt: => except Exception as e:
    if there is KeyboardInterrupt, the code did't run and stop.
    follow message [FileNotFoundError: [Errno 2] No such file or directory: 'weights.pkl']