Logstash LoadError: no such file to load — i18n

LoadError: no such file to load -- i18n
 require at org/jruby/RubyKernel.java:1085
 (root) at /usr/local/Cellar/logstash/1.4.2/libexec/lib/logstash/runner.rb:46

I received this error when trying to run logstash from within a Ruby script for automated integration test purposes. Turns out the ‘RUBYOPT’ environment variable was getting set, most likely by bundler, causing the issue. I simply cleared the env var before executing logstash:

RUBYOPT='' logstash -e '{config}'

or

unset RUBYOPT && logstash -e '{config}'