I’m writing this as more of a note to myself than to you. In Ruby GEM_PATH environment variable is where rubygems will look for installed gems. Hidden in in the docs is:

RubyGems’ default local repository can be overridden with the GEM_PATH and GEM_HOME environment variables. GEM_HOME sets the default repository to install into. GEM_PATH allows multiple local repositories to be searched for gems.

On Heroku we can see it used by calling env:

$ env
# ...
GEM_PATH=/app/vendor/bundle/ruby/2.1.1:vendor/bundle/ruby/1.9.1

The second part is for legacy reasons. In the case of codetriage, the first part is where our gems are stored.

This is what the directory structure looks like:

$ ls /app/vendor/bundle/ruby/2.1.1
bin  build_info  bundler  doc  extensions  gems  specifications

You don’t actually point GEM_PATH at the < directory >/gems path but rather the top level dir where bin/, doc/, and gems/ all live. It might be stupid to write down, but it’s been confusing to me more than a few times.

Hopes this helps future me.