无法停用conda

Question

我之前多次停用conda，但是突然出现一个错误，使我无法做任何事情：

$ conda deactivate
Error processing line 1 of /home/username/anaconda3/lib/python3.7/site-packages/matplotlib-3.0.3-py3.7-nspkg.pth:

  Traceback (most recent call last):
    File "/home/username/anaconda3/lib/python3.7/site.py", line 168, in addpackage
      exec(line)
    File "<string>", line 1, in <module>
    File "<frozen importlib._bootstrap>", line 580, in module_from_spec
  AttributeError: 'NoneType' object has no attribute 'loader'

Remainder of file ignored

这是什么意思，我该如何解决？