Le défaut d'installation de Nokogiri gem

Je suis en train de travailler sur une application rails qui permet des images en pièces jointes à chaque utilisation du compte. Je suis à l'aide d'un trombone, et amazon web services:

gem 'paperclip'
gem 'aws-sdk'

Quand je lance le bundle install, j'obtiens ce message:

extconf échoué, code de sortie 1

Gem files will remain installed in /usr/local/rvm/gems/ruby-2.1.2/gems/nokogiri-1.6.5 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.1.2/extensions/x86_64-darwin-13/2.1.0-static/nokogiri-1.6.5/gem_make.out
An error occurred while installing nokogiri (1.6.5), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.5'` succeeds before bundling.

Lorsque j'essaie de l'exécution "gem install nokogiri', j'obtiens ce message:

extconf échoué, code de sortie 1

Gem files will remain installed in /usr/local/rvm/gems/ruby-2.1.2/gems/nokogiri-1.6.5 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.1.2/extensions/x86_64-darwin-13/2.1.0-static/nokogiri-1.6.5/gem_make.out

Mon système d'exploitation est Mac OS X Mavericks 10.9.4. Ce qui se passe ici? Comment puis-je obtenir nokogiri à installer et à se comporter correctement?

Plein de trace de pile:

Building native extensions with: '--use-system-libraries'
This could take a while...
ERROR:  Error installing nokogiri:
ERROR: Failed to build gem native extension.
/usr/local/rvm/rubies/ruby-2.1.2/bin/ruby extconf.rb --use-system-libraries
checking if the C compiler accepts ... yes
checking if the C compiler accepts -Wno-error=unused-command-line-argument-hard-error-in-future... yes
Building nokogiri using system libraries.
libxml2 version 2.6.21 or later is required!
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/local/rvm/rubies/ruby-2.1.2/bin/ruby
--help
--clean
--use-system-libraries
--with-zlib-dir
--without-zlib-dir
--with-zlib-include
--without-zlib-include=${zlib-dir}/include
--with-zlib-lib
--without-zlib-lib=${zlib-dir}/lib
--with-xml2-dir
--without-xml2-dir
--with-xml2-include
--without-xml2-include=${xml2-dir}/include
--with-xml2-lib
--without-xml2-lib=${xml2-dir}/lib
--with-libxml-2.0-config
--without-libxml-2.0-config
--with-pkg-config
--without-pkg-config
--with-xslt-dir
--without-xslt-dir
--with-xslt-include
--without-xslt-include=${xslt-dir}/include
--with-xslt-lib
--without-xslt-lib=${xslt-dir}/lib
--with-libxslt-config
--without-libxslt-config
--with-exslt-dir
--without-exslt-dir
--with-exslt-include
--without-exslt-include=${exslt-dir}/include
--with-exslt-lib
--without-exslt-lib=${exslt-dir}/lib
--with-libexslt-config
--without-libexslt-config
extconf failed, exit code 1
Gem files will remain installed in /usr/local/rvm/gems/ruby-2.1.2/gems/nokogiri-1.6.5 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.1.2/extensions/x86_64-darwin-13/2.1.0-static/nokogiri-1.6.5/gem_make.out