jupyter xxx is not UTF-8 encoded

[mattshma]

打开文件时报错：

Error! /path/to/file.py is not UTF-8 encoded
Saving disabled.
See console for more details.

通过 vim 打开文件，输入：:set fileencoding，可看到文件编码。非 utf-8 文件打开时会报这个错误。