打开jupyter突然报错：
An unknown error occurred while loading this notebook. This version can load notebook formats v4 or earlier. See the server log for details.
我是这样解决：
rm ~/.ipython/profile_default/history.sqlite
参考：http://stackoverflow.com/questions/34960020/ipython-notebook-error-error-loading-notebook
IPython Notebook error: Error loading notebook
原文：http://www.cnblogs.com/shixiangwan/p/6860791.html