title: Rake error :warning: already initialized constant MAJOR
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/7319262/problem-to-run-comand-rake">Problem to run comand rake</a>  </p>
  </blockquote>
  
  
  
  <pre><code>yulong@ubuntu:~/depotnew$ rake db:migrate
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/version.rb:4: warning: already initialized constant MAJOR
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/version.rb:5: warning: already initialized constant MINOR
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/version.rb:6: warning: already initialized constant BUILD
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/version.rb:3: warning: already initialized constant NUMBERS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/version.rb:9: warning: already initialized constant VERSION
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake.rb:26: warning: already initialized constant RAKEVERSION
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/early_time.rb:17: warning: already initialized constant EARLY
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/alt_system.rb:32: warning: already initialized constant WINDOWS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/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
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/task_arguments.rb:73: warning: already initialized constant EMPTY_TASK_ARGS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/invocation_chain.rb:49: warning: already initialized constant EMPTY
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_utils.rb:10: warning: already initialized constant RUBY
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_utils.rb:84: warning: already initialized constant LN_SUPPORTED
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/dsl_definition.rb:143: warning: already initialized constant Commands
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:44: warning: already initialized constant ARRAY_METHODS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:47: warning: already initialized constant MUST_DEFINE
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:51: warning: already initialized constant MUST_NOT_DEFINE
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:55: warning: already initialized constant SPECIAL_RETURN
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:61: warning: already initialized constant DELEGATING_METHODS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:364: warning: already initialized constant DEFAULT_IGNORE_PATTERNS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake/file_list.rb:370: warning: already initialized constant DEFAULT_IGNORE_PROCS
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake.rb:64: warning: already initialized constant FileList
  /home/yulong/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2/lib/rake.rb:65: warning: already initialized constant RakeFileUtils
  rake aborted!
  stack level too deep
  </code></pre>
  
  <p>After i input:<strong>bundle exec bash</strong>,it works, why??</p>