MAC use brew to install opencv, look up information when a blog said the need to add the command:

brew tap homebrew/science

always gives an error when trying:

Error: homebrew/science was deprecated. This tap is now empty as all its formulae were migrated.

, meaning homebrew/science has been removed, meaning that the brew tap step is not required.

solution: remove this step, directly brew install xx, xx refers to your package.

above.