When installing Python packages on OSX Mavericks there will be a Clang error akin to this: clang: error: unknown argument: '-mno-fused-madd' To bypass this you need to tell Clang to ignore unknown flags So far this problem has occured with xattr and PIL/pilow but this command fixed both
sudo ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future pip install pillow