Building native extensions. This could take a while...
ERROR: Error installing libxml-ruby:
ERROR: Failed to build gem native extension.
/usr/local/rvm/rubies/ruby-2.2.0/bin/ruby -r ./siteconf20150608-66572-6mmes4.rb extconf.rb
* 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:
extconf.rb:17:in `': uninitialized constant Config (NameError)
extconf failed, exit code 1
Gem files will remain installed in /usr/local/rvm/gems/ruby-2.2.0/gems/libxml-ruby-2.6.0 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.2.0/extensions/x86_64-darwin-13/2.2.0/libxml-ruby-2.6.0/gem_make.out