Bug report

Bug summary

pydoc matplotlib.patches emits many warnings about the deprecation of validJoin and validCap. attn @brunobeltran, I guess.

Code for reproduction
Actual outcome

Per the above.

Expected outcome

No warning

Matplotlib version

• Operating system:
• Matplotlib version: master
• Matplotlib backend (print(matplotlib.get_backend())):
• Python version: 39
• Jupyter version (if applicable):
• Other libraries:

I guess a solution would be to add a check in _deprecated_property.__get__ to silence the warning if sys.argv[0] == pydoc.__file__.