ninja-win.zip saved to CWD but later opened/removed from script dir FileNotFoundError when running preconfigure.py from outside repo root (Windows) Download to sys.path[0]/ninja-win.zip and extract from the same path. Undefined exception variable in download failure path NameError that hides the real download failure Use except Exception as e: and print the actual exception. Module archives saved to CWD but later opened/removed from script dir FileNotFoundError for non-git source distributions or when using URL downloads from outside repo root Download to sys.path[0] (expected filepath). Zip files not closed after extraction Potential file-handle leaks / Windows file lock issues Use context managers (with ZipFile(...) as zipf). Built ninja copied to . instead of script dir (non-Windows) meson.py expects sys.path[0]/ninja, which can break if invoked from another working directory Copy to sys.path[0]/ninja.