uninitialized constant RailsAdmin on Ruby 2.2.1

ググってもそれらしいのは出てこなかったのでここに貼っておく。

Ruby 2.2.1 で 手元の Rails アプリをデプロイ中にエラー。 Ruby 2.1.5 だと起きない。

```shell-session
$ rbenv global
2.2.1
$ RAILS_RELATIVE_URL_ROOT=/myapp RAILS_ENV=production rbenv rake assets:precompile
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/activesupport-4.0.4/lib/active_support/values/time_zone.rb:283: warning: circular argument reference - now
WARNING: Nokogiri was built against LibXML version 2.7.6, but has dynamically loaded 2.8.0
rake aborted!
uninitialized constant RailsAdmin
/var/www/myapp/releases/20150315125732/config/initializers/rails_admin.rb:3:in `<top (required)>'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/engine.rb:609:in `block (2 levels) in <class:Engine>'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/engine.rb:608:in `each'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/engine.rb:608:in `block in <class:Engine>'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/initializable.rb:30:in `instance_exec'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/initializable.rb:30:in `run'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/initializable.rb:55:in `block in run_initializers'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/initializable.rb:44:in `each'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/initializable.rb:44:in `tsort_each_child'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/initializable.rb:54:in `run_initializers'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/application.rb:215:in `initialize!'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/railtie/configurable.rb:30:in `method_missing'
/var/www/myapp/releases/20150315125732/config/environment.rb:7:in `<top (required)>'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/application.rb:189:in `require_environment!'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/railties-4.0.4/lib/rails/application.rb:250:in `block in run_tasks_blocks'
/var/www/myapp/shared/bundle/ruby/2.2.0/gems/sprockets-rails-2.0.1/lib/sprockets/rails/task.rb:54:in `block (2 levels) in define'
Tasks: TOP => environment
(See full trace by running task with --trace)
$
```





```Gemfile.lock
GEM
  remote: https://rubygems.org/
  specs:
    actionmailer (4.0.4)
      actionpack (= 4.0.4)
      mail (~> 2.5.4)
    actionpack (4.0.4)
      activesupport (= 4.0.4)
      builder (~> 3.1.0)
      erubis (~> 2.7.0)
      rack (~> 1.5.2)
      rack-test (~> 0.6.2)
    active_decorator (0.3.4)
    activemodel (4.0.4)
      activesupport (= 4.0.4)
      builder (~> 3.1.0)
    activerecord (4.0.4)
      activemodel (= 4.0.4)
      activerecord-deprecated_finders (~> 1.0.2)
      activesupport (= 4.0.4)
      arel (~> 4.0.0)
    activerecord-deprecated_finders (1.0.3)
    activesupport (4.0.4)
      i18n (~> 0.6, >= 0.6.9)
      minitest (~> 4.2)
      multi_json (~> 1.3)
      thread_safe (~> 0.1)
      tzinfo (~> 0.3.37)
    addressable (2.3.5)
    anbt-sql-formatter (0.0.2)
    arel (4.0.2)
    atomic (1.1.16)
    awesome_print (1.2.0)
    bcrypt (3.1.7)
    builder (3.1.4)
    byebug (2.7.0)
      columnize (~> 0.3)
      debugger-linecache (~> 1.2)
    capistrano (3.1.0)
      i18n
      rake (>= 10.0.0)
      sshkit (~> 1.3)
    capistrano-bundler (1.1.2)
      capistrano (~> 3.0)
      sshkit (~> 1.2)
    capistrano-rails (1.1.1)
      capistrano (~> 3.1)
      capistrano-bundler (~> 1.1)
    capistrano-rsync (1.0.2)
      capistrano (>= 3.0.0.pre14, < 4)
    capybara (2.2.1)
      mime-types (>= 1.16)
      nokogiri (>= 1.3.3)
      rack (>= 1.0.0)
      rack-test (>= 0.5.4)
      xpath (~> 2.0)
    capybara-email (2.3.0)
      capybara (~> 2.2.0)
      mail
    celluloid (0.15.2)
      timers (~> 1.1.0)
    celluloid-io (0.15.0)
      celluloid (>= 0.15.0)
      nio4r (>= 0.5.0)
    climate_control (0.0.3)
      activesupport (>= 3.0)
    cocaine (0.5.3)
      climate_control (>= 0.0.3, < 1.0)
    coderay (1.1.0)
    coffee-rails (4.0.1)
      coffee-script (>= 2.2.0)
      railties (>= 4.0.0, < 5.0)
    coffee-script (2.2.0)
      coffee-script-source
      execjs
    coffee-script-source (1.7.0)
    columnize (0.3.6)
    coolline (0.4.3)
    database_rewinder (0.0.3)
    debugger-linecache (1.2.0)
    devise (3.2.4)
      bcrypt (~> 3.0)
      orm_adapter (~> 0.1)
      railties (>= 3.2.6, < 5)
      thread_safe (~> 0.1)
      warden (~> 1.2.3)
    diff-lcs (1.2.5)
    domain_name (0.5.16)
      unf (>= 0.0.5, < 1.0.0)
    erubis (2.7.0)
    execjs (2.0.2)
    factory_girl (4.4.0)
      activesupport (>= 3.0.0)
    factory_girl_rails (4.4.1)
      factory_girl (~> 4.4.0)
      railties (>= 3.0.0)
    faker (1.3.0)
      i18n (~> 0.5)
    ffi (1.9.6)
    figaro (0.7.0)
      bundler (~> 1.0)
      rails (>= 3, < 5)
    font-awesome-rails (4.0.3.1)
      railties (>= 3.2, < 5.0)
    formatador (0.2.4)
    guard (2.5.1)
      formatador (>= 0.2.4)
      listen (~> 2.6)
      lumberjack (~> 1.0)
      pry (>= 0.9.12)
      thor (>= 0.18.1)
    guard-rspec (4.2.8)
      guard (~> 2.1)
      rspec (>= 2.14, < 4.0)
    guard-spring (0.0.4)
      guard
      spring
    haml (4.0.5)
      tilt
    hashie (2.0.5)
    hike (1.2.3)
    hirb (0.7.1)
    hirb-unicode (0.0.5)
      hirb (~> 0.5)
      unicode-display_width (~> 0.1.1)
    html5_validators (1.1.2)
    http-cookie (1.0.2)
      domain_name (~> 0.5)
    i18n (0.6.9)
    i18n_generators (1.2.1)
      mechanize
      rails (>= 3.0.0)
    jbuilder (1.5.3)
      activesupport (>= 3.0.0)
      multi_json (>= 1.2.0)
    jquery-rails (3.1.0)
      railties (>= 3.0, < 5.0)
      thor (>= 0.14, < 2.0)
    jquery-ui-rails (4.2.0)
      railties (>= 3.2.16)
    json (1.8.1)
    kaminari (0.15.1)
      actionpack (>= 3.0.0)
      activesupport (>= 3.0.0)
    launchy (2.4.2)
      addressable (~> 2.3)
    libv8 (3.16.14.3)
    listen (2.7.1)
      celluloid (>= 0.15.2)
      celluloid-io (>= 0.15.0)
      rb-fsevent (>= 0.9.3)
      rb-inotify (>= 0.9)
    lumberjack (1.0.4)
    mail (2.5.4)
      mime-types (~> 1.16)
      treetop (~> 1.4.8)
    mecab (0.996)
    mechanize (2.7.2)
      domain_name (~> 0.5, >= 0.5.1)
      http-cookie (~> 1.0.0)
      mime-types (~> 1.17, >= 1.17.2)
      net-http-digest_auth (~> 1.1, >= 1.1.1)
      net-http-persistent (~> 2.5, >= 2.5.2)
      nokogiri (~> 1.4)
      ntlm-http (~> 0.1, >= 0.1.1)
      webrobots (>= 0.0.9, < 0.2)
    method_source (0.8.2)
    migrant (1.5.0)
      faker
      rails (>= 3.0.0)
      term-ansicolor
    mime-types (1.25.1)
    mini_portile (0.5.2)
    minitest (4.7.5)
    multi_json (1.9.0)
    mysql2 (0.3.15)
    nested_form (0.3.2)
    net-http-digest_auth (1.4)
    net-http-persistent (2.9.4)
    net-scp (1.1.2)
      net-ssh (>= 2.6.5)
    net-ssh (2.8.0)
    nio4r (1.0.0)
    nokogiri (1.6.1)
      mini_portile (~> 0.5.0)
    ntlm-http (0.1.1)
    orm_adapter (0.5.0)
    paperclip (4.1.1)
      activemodel (>= 3.0.0)
      activesupport (>= 3.0.0)
      cocaine (~> 0.5.3)
      mime-types
    polyglot (0.3.4)
    pry (0.9.12.6)
      coderay (~> 1.0)
      method_source (~> 0.8)
      slop (~> 3.4)
    pry-byebug (1.3.2)
      byebug (~> 2.7)
      pry (~> 0.9.12)
    pry-coolline (0.2.4)
      coolline (~> 0.3)
    pry-doc (0.6.0)
      pry (~> 0.9)
      yard (~> 0.8)
    pry-rails (0.3.2)
      pry (>= 0.9.10)
    quiet_assets (1.0.2)
      railties (>= 3.1, < 5.0)
    rack (1.5.2)
    rack-mini-profiler (0.9.1)
      rack (>= 1.1.3)
    rack-pjax (0.7.0)
      nokogiri (~> 1.5)
      rack (~> 1.3)
    rack-test (0.6.2)
      rack (>= 1.0)
    rails (4.0.4)
      actionmailer (= 4.0.4)
      actionpack (= 4.0.4)
      activerecord (= 4.0.4)
      activesupport (= 4.0.4)
      bundler (>= 1.3.0, < 2.0)
      railties (= 4.0.4)
      sprockets-rails (~> 2.0.0)
    rails-flog (1.3.1)
      anbt-sql-formatter
      awesome_print
      rails (>= 3.2.0)
    rails_12factor (0.0.2)
      rails_serve_static_assets
      rails_stdout_logging
    rails_admin (0.6.1)
      builder (~> 3.1)
      coffee-rails (~> 4.0)
      font-awesome-rails (>= 3.0)
      haml (~> 4.0)
      jquery-rails (~> 3.0)
      jquery-ui-rails (~> 4.0)
      kaminari (~> 0.14)
      nested_form (~> 0.3)
      rack-pjax (~> 0.7)
      rails (~> 4.0)
      remotipart (~> 1.0)
      safe_yaml (~> 1.0)
      sass-rails (~> 4.0)
    rails_serve_static_assets (0.0.2)
    rails_stdout_logging (0.0.3)
    railties (4.0.4)
      actionpack (= 4.0.4)
      activesupport (= 4.0.4)
      rake (>= 0.8.7)
      thor (>= 0.18.1, < 2.0)
    rake (10.1.1)
    rake_shared_context (0.2.0)
    rb-fsevent (0.9.4)
    rb-inotify (0.9.3)
      ffi (>= 0.5.0)
    rb-readline (0.5.1)
    rdoc (4.1.1)
      json (~> 1.4)
    ref (1.0.5)
    remotipart (1.2.1)
    rspec (2.14.1)
      rspec-core (~> 2.14.0)
      rspec-expectations (~> 2.14.0)
      rspec-mocks (~> 2.14.0)
    rspec-core (2.14.8)
    rspec-expectations (2.14.5)
      diff-lcs (>= 1.1.3, < 2.0)
    rspec-mocks (2.14.6)
    rspec-rails (2.14.1)
      actionpack (>= 3.0)
      activemodel (>= 3.0)
      activesupport (>= 3.0)
      railties (>= 3.0)
      rspec-core (~> 2.14.0)
      rspec-expectations (~> 2.14.0)
      rspec-mocks (~> 2.14.0)
    safe_yaml (1.0.1)
    sass (3.2.16)
    sass-rails (4.0.2)
      railties (>= 4.0.0, < 5.0)
      sass (~> 3.2.0)
      sprockets (~> 2.8, <= 2.11.0)
      sprockets-rails (~> 2.0.0)
    sdoc (0.4.0)
      json (~> 1.8)
      rdoc (~> 4.0, < 5.0)
    settingslogic (2.0.9)
    shoulda-matchers (2.5.0)
      activesupport (>= 3.0.0)
    simple_form (3.0.1)
      actionpack (>= 4.0.0, < 4.1)
      activemodel (>= 4.0.0, < 4.1)
    slop (3.5.0)
    spring (1.1.2)
    spring-commands-rspec (1.0.1)
      spring (>= 0.9.1)
    sprockets (2.11.0)
      hike (~> 1.2)
      multi_json (~> 1.0)
      rack (~> 1.0)
      tilt (~> 1.1, != 1.3.0)
    sprockets-rails (2.0.1)
      actionpack (>= 3.0)
      activesupport (>= 3.0)
      sprockets (~> 2.8)
    sshkit (1.3.0)
      net-scp (>= 1.1.2)
      net-ssh
      term-ansicolor
    term-ansicolor (1.3.0)
      tins (~> 1.0)
    therubyracer (0.12.1)
      libv8 (~> 3.16.14.0)
      ref
    thor (0.18.1)
    thread_safe (0.3.4)
      atomic (>= 1.1.7, < 2)
    tilt (1.4.1)
    timers (1.1.0)
    tins (1.0.0)
    treetop (1.4.15)
      polyglot
      polyglot (>= 0.3.1)
    turbolinks (2.2.1)
      coffee-rails
    tzinfo (0.3.39)
    uglifier (2.5.0)
      execjs (>= 0.3.0)
      json (>= 1.8.0)
    unf (0.1.3)
      unf_ext
    unf_ext (0.0.6)
    unicode-display_width (0.1.1)
    warden (1.2.3)
      rack (>= 1.0)
    webrobots (0.1.1)
    xpath (2.0.0)
      nokogiri (~> 1.3)
    yard (0.8.7.3)

PLATFORMS
  ruby

DEPENDENCIES
  active_decorator
  awesome_print
  capistrano (~> 3.1.0)
  capistrano-bundler
  capistrano-rails
  capistrano-rsync
  capybara
  capybara-email
  coffee-rails (~> 4.0.0)
  database_rewinder
  devise
  factory_girl_rails
  figaro
  guard-rspec
  guard-spring
  hashie
  hirb
  hirb-unicode
  html5_validators
  i18n_generators
  jbuilder (~> 1.2)
  jquery-rails
  jquery-ui-rails
  kaminari
  launchy
  mecab
  migrant
  mysql2
  nokogiri
  paperclip (~> 4.1)
  pry-byebug
  pry-coolline
  pry-doc
  pry-rails
  quiet_assets
  rack-mini-profiler
  rails (= 4.0.4)
  rails-flog
  rails_12factor
  rails_admin
  rake_shared_context
  rb-readline
  rspec-rails
  sass-rails (~> 4.0.0)
  sdoc
  settingslogic
  shoulda-matchers
  simple_form
  spring
  spring-commands-rspec
  therubyracer
  turbolinks
  uglifier (>= 1.3.0)
```