Building native extensions. This could take a while...
ERROR: Error installing compass:
ERROR: Failed to build gem native extension.
current directory: /Library/Ruby/Gems/2.0.0/gems/ffi-1.9.17/ext/ffi_c
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -r ./siteconf20170302-3213-i36x9b.rb extconf.rb
mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/include/ruby.h
extconf failed, exit code 1
Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/ffi-1.9.17 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-16/2.0.0/ffi-1.9.17/gem_make.out
Building native extensions. This could take a while...
[[ASuccessfully installed ffi-1.9.17
Fetching: rb-inotify-0.9.8.gem (100%)
Successfully installed rb-inotify-0.9.8
Fetching: compass-1.0.3.gem (100%)
ERROR: While executing gem ... (Errno::EPERM)
Operation not permitted - /usr/bin/compass