I was trying to build a snap for ethereum's mist. It uses yarn as the package manager, but it has an entry in package.json that we don't support: "postinstall": "cd interface && yarn" https://github.com/ethereum/mist/blob/develop/package.json#L11 Trying to build this snap will fail with: error /home/elopio/mist/parts/mist/src/node_modules/Mist: Command failed. Exit code: 127 Command: sh Arguments: -c cd interface && yarn Directory: /home/elopio/mist/parts/mist/src/node_modules/Mist Output: sh: 1: yarn: not found In order to support this use case, during the pull and build, the commands need to be able to execute parts/<name>/bin/yarn.