I'm using Nixpacks and added python3 to the nixPkgs in the setup phase. It looks like it's installed, but when my app runs, it still throws /bin/sh: 1: python3: not found. Any idea why python3 isn’t available at runtime, even though it's in the Nixpacks config?

[phases.setup]
nixPkgs = ["...", "python3"]

providers = ["...", "python"]

[start]
cmd = "PATH=$PATH:/root/.nix-profile/bin npm start"