Hi, I am trying to setup a Python 3 cctbx. I did python bootstrap.py --git-ssh --python3 --builder cctbxlite But it fails at the installation of OpenSSL. Clang version is "Apple LLVM version 10.0.1 (clang-1001.0.46.4)”. I attached the OpenSSL install log but I don’t see any error in it. And the advice to run xcode-select is bogus: I have it already setup. Best wishes, Luc Installing OpenSSL... log file is /Users/luc/Developer/cctbx/base_tmp/OpenSSL_install_log getting package openssl-1.0.2r.tar.gz... downloading from https://gitcdn.link/repo/dials/dependencies/master/openssl-1.0.2r.tar.gz : 5223 kB installing openssl-1.0.2r.tar.gz... package openssl took 219.5s to install -------------------------------------------------------------------------------- zlib.h missing -- try running 'xcode-select --install' first Process failed with return code 1