title: GitHub for Mac error: git: 'credential-osxkeychain' is not a git command
body: <p>When using the GitHub for Mac app (version 87), I received the following error:</p>
  
  <blockquote>
    <p>git: 'credential-osxkeychain' is not a git command. See 'git --help'.</p>
    
    <p>error: The requested URL returned error: 403 while accessing https://github.com/[PROJECT URL]/info/refs</p>
    
    <p>fatal: HTTP request failed (256)</p>
  </blockquote>
  
  <p>The git command-line tools (version 1.8.0) are installed at <code>/usr/local/git/bin</code> and git-credential-osxkeychain was correctly installed at <code>/usr/local/git/bin</code>.</p>
  
  <p>How can I solve this error?</p>