直升机，
我正在尝试使用 mysql2 gem 为我的 rails 3 应用程序运行 rake db:migrate。但最终出现以下错误。你有什么主意吗？谢谢
WARNING: This version of mysql2 (0.3.7) doesn't ship with the ActiveRecord adapter bundled anymore as it's now part of Rails 3.1
WARNING: Please use the 0.2.x releases if you plan on using it in Rails <= 3.0.x
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:4: warning: already initialized constant MAJOR
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:5: warning: already initialized constant MINOR
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:6: warning: already initialized constant BUILD
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:3: warning: already initialized constant NUMBERS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:9: warning: already initialized constant VERSION
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake.rb:26: warning: already initialized constant RAKEVERSION
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/early_time.rb:17: warning: already initialized constant EARLY
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/alt_system.rb:32: warning: already initialized constant WINDOWS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/application.rb:28: warning: already initialized constant DEFAULT_RAKEFILES
WARNING: Possible conflict with Rake extension: String#ext already exists
WARNING: Possible conflict with Rake extension: String#pathmap already exists
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/task_arguments.rb:73: warning: already initialized constant EMPTY_TASK_ARGS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/invocation_chain.rb:49: warning: already initialized constant EMPTY
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_utils.rb:10: warning: already initialized constant RUBY
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_utils.rb:84: warning: already initialized constant LN_SUPPORTED
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/dsl_definition.rb:143: warning: already initialized constant Commands
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:44: warning: already initialized constant ARRAY_METHODS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:47: warning: already initialized constant MUST_DEFINE
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:51: warning: already initialized constant MUST_NOT_DEFINE
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:55: warning: already initialized constant SPECIAL_RETURN
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:61: warning: already initialized constant DELEGATING_METHODS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:364: warning: already initialized constant DEFAULT_IGNORE_PATTERNS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:370: warning: already initialized constant DEFAULT_IGNORE_PROCS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake.rb:64: warning: already initialized constant FileList
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake.rb:65: warning: already initialized constant RakeFileUtils
rake aborted!
stack level too deep