Stopping spewing moany messages at me. Let’s sort this one.

Robs-MacBook-Pro:project rl$ rails c
WARNING: Nokogiri was built against LibXML version 2.9.4, but has dynamically loaded 2.9.12
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Robs-MacBook-Pro:project rl$ cat Gemfile | grep nokogiri
gem 'nokogiri', '1.9.1'
Robs-MacBook-Pro:project rl$ gem install nokogiri -v 1.9.1 -- --with-xml2-dir=/usr --with-xslt-dir=/opt/local --with-iconv-dir=/opt/local
Building native extensions with: '--with-xml2-dir=/usr --with-xslt-dir=/opt/local --with-iconv-dir=/opt/local'
This could take a while...
Successfully installed nokogiri-1.9.1
1 gem installed

Now it’s compiled against these liibrary locations…

Robs-MacBook-Pro:project rl$ rails c
Loading development environment (Rails 4.2.11.3)
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And done….