title: composer error: Installation failed, reverting ./composer.json to its original content
body: <p>I try install <a href="https://github.com/google/google-api-php-client" rel="nofollow">https://github.com/google/google-api-php-client</a> for my php project via composer.</p>
  
  <p>composer.json:</p>
  
  <pre><code>{
      "require": {
          "Intervention/image": "~2.3.7",
          "intervention/image": "^2.3",
          "guzzlehttp/guzzle": "^6.2" 
      }
  }
  </code></pre>
  
  <p>I run this command:</p>
  
  <pre><code>composer require google/apiclient:^2.0
  </code></pre>
  
  <p>And result:</p>
  
  <pre><code>./composer.json has been updated
  Loading composer repositories with package information
  Updating dependencies (including require-dev)
  Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - google/apiclient v2.0.0 requires google/auth 0.8 -&gt; satisfiable by google/auth[v0.8].
      - Installation request for google/apiclient 2.0 -&gt; satisfiable by google/apiclient[v2.0.0].
      - Conclusion: remove guzzlehttp/psr7 1.3.0
      - Conclusion: don't install guzzlehttp/psr7 1.3.0
      - google/auth v0.8 requires guzzlehttp/psr7 1.2.* -&gt; satisfiable by guzzlehttp/psr7[1.2.0, 1.2.1, 1.2.2, 1.2.3].
      - Can only install one of: guzzlehttp/psr7[1.2.0, 1.3.0].
      - Can only install one of: guzzlehttp/psr7[1.2.1, 1.3.0].
      - Can only install one of: guzzlehttp/psr7[1.2.2, 1.3.0].
      - Can only install one of: guzzlehttp/psr7[1.2.3, 1.3.0].
      - Installation request for guzzlehttp/psr7 (locked at 1.3.0) -&gt; satisfiable by guzzlehttp/psr7[1.3.0].
  
  
  Installation failed, reverting ./composer.json to its original content.
  </code></pre>
  
  <p>Also I installed <code>php composer.phar require guzzlehttp/guzzle</code> before...</p>