bug : No module named 'six

Traceback (most recent call last):
  File "D:\Anaconda\Scripts\jupyter-notebook-script.py", line 6, in <module>
    from notebook.notebookapp import main
  File "D:\Anaconda\lib\site-packages\notebook\__init__.py", line 25, in <module>
    from .nbextensions import install_nbextension
  File "D:\Anaconda\lib\site-packages\notebook\nbextensions.py", line 31, in <module>
    from .config_manager import BaseJSONConfigManager
  File "D:\Anaconda\lib\site-packages\notebook\config_manager.py", line 14, in <module>
    from six import PY3
ModuleNotFoundError: No module named 'six'

目前不知道哪裏出錯了。。。