Installing opencv on macOS
$ brew install opencv --ignore-dependencies
$ brew install tbb
$ brew install openblas
$ brew install ffmpeg
$ brew install ilmbase
$ brew install openexr
$ pip install numpy
$ ln -s /usr/local/opt/opencv/lib/python3.7/site-packages/cv2/python-3.7/cv2.cpython-37m-darwin.so $HOME/.pyenv/versions/3.7.2/lib/python3.7/site-package