title: Pod init error tool 'xcodebuild' requires Xcode
body: <p>Im trying to run <code>pod init</code> command on my new project. 
  It has never happened to me before. The things I have tried to fix it are:</p>
  
  <ul>
  <li>Closing Xcode</li>
  <li>Creating a new project</li>
  <li>Restarting my computer</li>
  </ul>
  
  <p>The error I get in the console is:</p>
  
  <pre><code>error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance 
  
  ### Command
  
  ```
  /usr/local/bin/pod init
  ```
  
  ### Report
  
  * What did you do?
  
  * What did you expect to happen?
  
  * What happened instead?
  
  
  ### Stack
  
  ```
     CocoaPods : 1.3.1
          Ruby : ruby 2.3.3p222 (2016-11-21 revision 56859) [universal.x86_64-darwin17]
      RubyGems : 2.5.2
          Host : Mac OS X 10.13.4 (17E199)
         Xcode :  ()
           Git : git version 2.15.1 (Apple Git-101)
  Ruby lib dir : /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib
  Repositories : master - https://github.com/CocoaPods/Specs.git @ ed5bf5bee99a1909bcc8fb8ffa39fb08d1af6bc8
  ```
  
  ### Plugins
  
  ```
  cocoapods-deintegrate : 1.0.1
  cocoapods-plugins     : 1.0.0
  cocoapods-search      : 1.0.0
  cocoapods-stats       : 1.0.0
  cocoapods-trunk       : 1.3.0
  cocoapods-try         : 1.1.0
  ```
  
  ### Error
  
  ```
  RuntimeError - [Xcodeproj] Unknown object version.
  /Library/Ruby/Gems/2.3.0/gems/xcodeproj-1.5.4/lib/xcodeproj/project.rb:217:in `initialize_from_file'
  /Library/Ruby/Gems/2.3.0/gems/xcodeproj-1.5.4/lib/xcodeproj/project.rb:102:in `open'
  /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.3.1/lib/cocoapods/command/init.rb:41:in `validate!'
  /Library/Ruby/Gems/2.3.0/gems/claide-1.0.2/lib/claide/command.rb:333:in `run'
  /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.3.1/lib/cocoapods/command.rb:52:in `run'
  /Library/Ruby/Gems/2.3.0/gems/cocoapods-1.3.1/bin/pod:55:in `&lt;top (required)&gt;'
  /usr/local/bin/pod:22:in `load'
  /usr/local/bin/pod:22:in `&lt;main&gt;'
  ```
  </code></pre>