Make `python` command refer to python2 again
Make `python` command refer to python2 again

Previously, /usr/local/opt/python/libexec/bin was added to PATH to use
Homebrew's python2 over the system python2. In recent Homebrew versions,
doing that makes `python` point to `python3` instead.

https://docs.brew.sh/Homebrew-and-Python:
> python3 points to Homebrew’s Python 3.x (if installed)
> python2 points to Homebrew’s Python 2.7.x (if installed)
> python points to Homebrew’s Python 2.7.x (if installed) otherwise
>   the macOS system Python. Check out brew info python if you
>   wish to add Homebrew’s 3.x python to your PATH.
> pip3 points to Homebrew’s Python 3.x’s pip (if installed)
> pip and pip2 point to Homebrew’s Python 2.7.x’s pip (if installed)

jensgreen/prezto