macOS ≥ 12.3 does not have python anymore

[fxcoudert]

Since macOS 12.3, there is no python executable: Python 2 was removed, and Python 3 is only available as python3. Therefore, building Julia (1.8.0-beta3) from source yields this error:

Creating usr/etc/julia/startup.jl
Copying in usr/share/man/man1/julia.1
/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/contrib/install.sh 755 /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/contrib/julia-config.jl /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/usr/share/julia/
Warning: git information unavailable; versioning information limited
env: python2: No such file or directory
env: python2: No such file or directory
mkdir -p /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/python2_path
/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/tools/jldownload /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/libwhich-81e9723c0273d78493dc8c8ed570f68d9ce7e89e.tar.gz https://api.github.com/repos/vtjnash/libwhich/tarball/81e9723c0273d78493dc8c8ed570f68d9ce7e89e
python -c 'import sys; sys.exit(not sys.version_info > (3, 0))' && \
	/usr/bin/env python2 -c 'import sys; sys.exit(not sys.version_info < (3, 0))' && \
	ln -sf  "/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/python2_path/python" && \
	ln -sf -config "/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/python2_path/python-config"
/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/tools/jldownload /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/blastrampoline-d32042273719672c6669f6442a0be5605d434b70.tar.gz https://api.github.com/repos/JuliaLinearAlgebra/libblastrampoline/tarball/d32042273719672c6669f6442a0be5605d434b70
/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/tools/jldownload /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/libuv-3a63bf71de62c64097989254e4f03212e3bf5fc8.tar.gz https://api.github.com/repos/JuliaLang/libuv/tarball/3a63bf71de62c64097989254e4f03212e3bf5fc8
/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/tools/jldownload /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/dsfmt-2.2.4.tar.gz https://github.com/MersenneTwister-Lab/dSFMT/archive/v2.2.4.tar.gz
/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/tools/jldownload /private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/llvm-julia-13.0.1-0.tar.gz https://api.github.com/repos/JuliaLang/llvm-project/tarball/julia-13.0.1-0
/bin/sh: python: command not found
make[2]: [/private/tmp/julia-20220430-38583-144297r/julia-1.8.0-beta3/deps/srccache/python2_path] Error 127 (ignored)

even if we specify PYTHON=python3 as an argument to make.

This does not appear to be blocking the build, but it's weird that it's a. searching for an outdated Python version, b. erroring out (even if it is ignored), c. not using the PYTHON argument passed to it. So I thought I'd report it.

[giordano]

I presume

julia/deps/llvm.mk

Line 197 in 6026b5f

# LLDB still relies on plenty of python 2.x infrastructure, without checking

is the reason why this is looking specifically for python 2, without using the PYTHON variable. Whether that comment is still true today, I have no idea.

[vchuravy]

I don't think it is anymore.