pipでハッシュが一致しないエラー

(penv0) pi@raspberrypi:~/Documents/py $ pip install opencv-python==3.4.11.41
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Collecting opencv-python==3.4.11.41
  Downloading https://www.piwheels.org/simple/opencv-python/opencv_python-3.4.11.41-cp37-cp37m-linux_armv7l.whl (9.3MB)
    92% |█████████████████████████████▊  | 8.6MB 20kB/s eta 0:00:34
THESE PACKAGES DO NOT MATCH THE HASHES FROM THE REQUIREMENTS FILE. If you have updated the package versions, please update the hashes. Otherwise, examine the package contents carefully; someone may have tampered with them.
    opencv-python==3.4.11.41 from https://www.piwheels.org/simple/opencv-python/opencv_python-3.4.11.41-cp37-cp37m-linux_armv7l.whl#sha256=7298c55e59f00b7f72a20621072b381a40cd3b4be03d07e60235949e98bd620f:
        Expected sha256 7298c55e59f00b7f72a20621072b381a40cd3b4be03d07e60235949e98bd620f
             Got        dd1a2a12a0c8147a42c0e44a52cbd73200d89427eed8766c784c1e422f35c5f1

なにこれ．

ハッシュがどうにも一致してないらしい． そこで

pip install https://www.piwheels.org/simple/opencv-python/opencv_python-3.4.11.41-cp37-cp37m-linux_armv7l.whl

を叩いたが失敗．うーん．

なので，

wget https://www.piwheels.org/simple/opencv-python/opencv_python-3.4.11.41-cp37-cp37m-linux_armv7l.whl

ってして

pip install opencv_python-3.4.11.41-cp37-cp37m-linux_armv7l.whl

ってしたらできた．