LoadError: Could not load 'active_record/connection_adapters/mysql2_adapter'

znkd 2015-10-14 12:25:18

hi,各位，我用macosx 10.10，安装gitlab。本人不熟悉ruby和rails等。还请大家给出指正，谢谢。
当执行 $ sudo -u git -H bundle exec rake gitlab:setup RAILS_ENV=production 的时候，报错如下图片：
rake aborted!
LoadError: Could not load 'active_record/connection_adapters/mysql2_adapter'. Make sure that the adapter in config/database.yml is valid. If you use an adapter other than 'mysql', 'mysql2', 'postgresql' or 'sqlite3' add the necessary adapter gem to the Gemfile.
/Users/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-4.1.11/lib/active_support/dependencies.rb:247:in `require'
/Users/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-4.1.11/lib/active_support/dependencies.rb:247:in `block in require'
/Users/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-4.1.11/lib/active_support/dependencies.rb:232:in `load_dependency'
/Users/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-4.1.11/lib/active_support/dependencies.rb:247:in `require'
/Users/git/gitlab/vendor/bundle/ruby/2.0.0/gems/mysql2-0.3.16/lib/mysql2.rb:8:in `<top (required)>'
......

我的相关文件和环境如下：
gemfile:
source "https://rubygems.org"
gem 'rails', '4.1.11'
# Specify a sprockets version due to security issue
# See https://groups.google.com/forum/#!topic/rubyonrails-security/doAVp0YaTqY
gem 'sprockets', '~> 2.12.3'
# Default values for AR models
gem "default_value_for", "~> 3.0.0"
# Supported DBs
gem "mysql2", group: :mysql
gem "pg", group: :postgres

gemfile.lock:
multi_xml (0.5.5)
multipart-post (1.2.0)
mysql2 (0.3.16)
net-ldap (0.11)
net-scp (1.2.1)
环境：
RubyGems Environment:
- RUBYGEMS VERSION: 2.4.8
- RUBY VERSION: 2.0.0 (2014-05-08 patchlevel 481) [universal.x86_64-darwin14]
- INSTALLATION DIRECTORY: /Library/Ruby/Gems/2.0.0
- RUBY EXECUTABLE: /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
- EXECUTABLE DIRECTORY: /usr/bin
- SPEC CACHE DIRECTORY: /Users/liu/.gem/specs
- SYSTEM CONFIGURATION DIRECTORY: /Library/Ruby/Site
- RUBYGEMS PLATFORMS:
- ruby
- universal-darwin-14
- GEM PATHS:
- /Library/Ruby/Gems/2.0.0
- /Users/liu/.gem/ruby/2.0.0
- /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/gems/2.0.0
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :backtrace => false
- :bulk_threshold => 1000
- :sources => ["https://ruby.taobao.org/"]
- REMOTE SOURCES:
- https://ruby.taobao.org/
- SHELL PATH:
- /usr/local/mysql/bin
- /usr/local/bin
- /usr/bin
- /bin
- /usr/sbin
- /sbin

config/database.yml 如下:
# PRODUCTION
#
production:
adapter: mysql2
encoding: utf8
collation: utf8_general_ci
reconnect: false
database: gitlabhq_production
pool: 10
username: git
password: youku12345
host: localhost
port: 3306
# socket: /tmp/mysql.sock

#
# Development specific
#
development:
adapter: mysql2
encoding: utf8
collation: utf8_general_ci
reconnect: false
database: gitlabhq_development
pool: 5
username: root
password: "secure password"
# socket: /tmp/mysql.sock

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test: &test
adapter: mysql2
encoding: utf8
collation: utf8_general_ci
reconnect: false
database: gitlabhq_test
pool: 5
username: root
password:
# socket: /tmp/mysql.sock

我的yml文件，用的adapter是mysql2，并且，gem list中也有mysql2，为什么还是报错呢？
请大家帮忙分析一下原因和解决方案，谢谢。因为我不是很熟悉ruby和rails，所以，麻烦大家给的方案稍微详细一下，3q～

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