Can't install an old version of libv8 (needed for swedemom's old ruby gems).
First I had to install Python 2 (with pyenv): https://stackoverflow.com/a/67274521
Then I wanted to run brew install v8@3.15 but got this error:
Error: v8@3.15 has been disabled because it depends on Python 2 to build!
Workaround is to undisable it (https://stackoverflow.com/a/73595534):
brew tap homebrew/core --force brew edit v8@3.15 # remove the "disable!" line pyenv global 2.7.18 # not just the current shell HOMEBREW_NO_INSTALL_FROM_API=1 brew install v8@3.15