没有（已安装的）软件包，Jupyter突然无法启动

Question

我在安装软件包时遇到问题。我取消了安装mid解决方案环境

现在，当我尝试打开Jupyter笔记本时，我收到以下错误：

Traceback (most recent call last):
  File "/Users/Me/opt/anaconda3/bin/jupyter-notebook", line 7, in <module>
    from notebook.notebookapp import main
  File "/Users/Me/opt/anaconda3/lib/python3.7/site-packages/notebook/notebookapp.py", line 80, in <module>
    from .services.contents.manager import ContentsManager
  File "/Users/Me/opt/anaconda3/lib/python3.7/site-packages/notebook/services/contents/manager.py", line 17, in <module>
    from nbformat import sign, validate as validate_nb, ValidationError
  File "/Users/Me/opt/anaconda3/lib/python3.7/site-packages/nbformat/__init__.py", line 32, in <module>
    from .validator import validate, ValidationError
  File "/Users/Me/opt/anaconda3/lib/python3.7/site-packages/nbformat/validator.py", line 23, in <module>
    raise ImportError(str(e) + verbose_msg)
ImportError: No module named 'importlib_metadata'

    Jupyter notebook format depends on the jsonschema package:

        https://pypi.python.org/pypi/jsonschema

    Please install it first.

我试图通过conda install安装jsonschema和importlib_metadata。当我做那个时，我收到这个（两个都是）：

# All requested packages already installed.

我试着一次又一次地关掉它；我试着移除并重新安装Jupyter。两者都不起作用。这令人感到非常沮丧。到底发生了什么事，为什么Jupyter在周末前工作正常，却突然决定不工作？更重要的是，我该如何解决这个问题