google-cloud-ruby: LoadError when using Unicorn and Nginx

Having a crash in production environment only on the require 'google/cloud/vision' line. This all works fine in development. What could I have wrong in production?

/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require’: No such file to load – google/gax (LoadError)

…

from /home/rails/app/services/cloud_vision.rb:5:in `<top (required)>’

app/services/cloud_vision.rb

# app/services/cloud_vision.rb

### this is for [google-cloud-vision gem](http://googlecloudplatform.github.io/google-cloud-ruby/#/docs/google-cloud-vision/master/google/cloud/vision)

require 'google/cloud/vision'
require 'base64'
require 'googleauth'
require 'open-uri'
class CloudVision
	
    def initialize
    ### vision service
	@vision = Google::Cloud::Vision.new
    end
#...
end

I have google-gax in my gemfile.lock

    google-cloud-core (0.21.1)
      googleauth (~> 0.5.1)
    google-cloud-vision (0.21.1)
      google-cloud-core (~> 0.21.0)
      google-gax (~> 0.6.0)
      google-protobuf (~> 3.0)
      googleapis-common-protos (~> 1.3)
      grpc (~> 1.0)
    google-gax (0.6.0)
      googleapis-common-protos (~> 1.3.1)
      googleauth (~> 0.5.1)
      grpc (~> 1.0)
      rly (~> 0.2.3)
    google-protobuf (3.0.2)
    googleapis-common-protos (1.3.4)
      google-protobuf (~> 3.0)
      grpc (~> 1.0)
    googleauth (0.5.1)
      faraday (~> 0.9)
      jwt (~> 1.4)
      logging (~> 2.0)
      memoist (~> 0.12)
      multi_json (~> 1.11)
      os (~> 0.9)
      signet (~> 0.7)

stack trace

/usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require': No such file to load -- google/gax (LoadError)
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/google-cloud-vision-0.21.1/lib/google/cloud/vision/v1/image_annotator_api.rb:28:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/google-cloud-vision-0.21.1/lib/google/cloud/vision/v1.rb:15:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/google-cloud-vision-0.21.1/lib/google/cloud/vision/service.rb:18:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/google-cloud-vision-0.21.1/lib/google/cloud/vision/project.rb:18:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/google-cloud-vision-0.21.1/lib/google/cloud/vision.rb:17:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /home/rails/app/services/cloud_vision.rb:5:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:360:in `require_or_load'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:317:in `depend_on'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:233:in `require_dependency'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/engine.rb:472:in `block (2 levels) in eager_load!'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/engine.rb:471:in `each'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/engine.rb:471:in `block in eager_load!'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/engine.rb:469:in `each'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/engine.rb:469:in `eager_load!'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/engine.rb:346:in `eager_load!'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/application/finisher.rb:56:in `each'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/application/finisher.rb:56:in `block in <module:Finisher>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:30:in `instance_exec'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:30:in `run'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:55:in `block in run_initializers'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `each'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `call'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:54:in `run_initializers'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.6/lib/rails/application.rb:352:in `initialize!'
	from /home/rails/config/environment.rb:5:in `<top (required)>'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from config.ru:4:in `block in <main>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:55:in `instance_eval'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:55:in `initialize'
	from config.ru:1:in `new'
	from config.ru:1:in `<main>'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn.rb:56:in `eval'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn.rb:56:in `block in builder'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:752:in `build_app!'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:617:in `init_worker_process'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:639:in `worker_loop'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:508:in `spawn_missing_workers'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:132:in `start'
	from /usr/local/rvm/gems/ruby-2.3.0/gems/unicorn-5.1.0/bin/unicorn:126:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.3.0/bin/unicorn:23:in `load'
	from /usr/local/rvm/gems/ruby-2.3.0/bin/unicorn:23:in `<main>'
	from /usr/local/rvm/gems/ruby-2.0.0-p353/bin/ruby_executable_hooks:15:in `eval'
	from /usr/local/rvm/gems/ruby-2.0.0-p353/bin/ruby_executable_hooks:15:in `<main>'