pip3 install opencv is looking at the wrong URL

I'm trying to install opencv with pip3 on my Devuan GNU/Linux 3, and this is what happens:

$ pip3 install opencv
Collecting opencv
Could not install packages due to an EnvironmentError: 404 Client Error: Not Found for url: https://pypi.org/simple/opencv 

and indeed, if you browse that URL, you get a 404 page. Why is this happening? Am I to blame? Devuan? pypi.org administrators? Somebody else? Also - can I replace the URL somehow? Or manually install from somewhere?