import matplotlib.pyplot as plt causes AttributeError: 'property' object has no attribute '__name__'

I have a Thinkpad Lenovo P72 with windows 10 and when I write: import matplotlib.pyplot as plt,

I obtain:

Python 3.6.8 (tags/v3.6.8:3c6b436a57, Dec 24 2018, 00:16:47) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib.pyplot as plt
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\n-bou\AppData\Roaming\Python\Python36\site-packages\matplotlib\pyplot.py", line 32, in <module>
    import matplotlib.colorbar
  File "C:\Users\n-bou\AppData\Roaming\Python\Python36\site-packages\matplotlib\colorbar.py", line 27, in <module>
    import matplotlib.artist as martist
  File "C:\Users\n-bou\AppData\Roaming\Python\Python36\site-packages\matplotlib\artist.py", line 57, in <module>
    class Artist:
  File "C:\Users\n-bou\AppData\Roaming\Python\Python36\site-packages\matplotlib\artist.py", line 64, in Artist
    @property
  File "C:\Users\n-bou\AppData\Roaming\Python\Python36\site-packages\matplotlib\cbook\deprecation.py", line 182, in deprecate
    name = obj.__name__
AttributeError: 'property' object has no attribute '__name__'

I use Python 3.6.8. Someone has any idea ? It worked well until yesterday, but I has to do many changes on my installation and now I obtain that.

Best, N.