title: "End-of-central-directory signature not found." when installing Xcode 8 beta xip file
body: <p>I've download the Xcode 8 beta .xip file. I cannot unzip. Opening the file just sits there for hours saying "Verifying..."</p>
  
  <p>If I try from command line I get the following... </p>
  
  <pre><code>Downloads unzip Xcode_8_beta.xip 
  Archive:  Xcode_8_beta.xip
    End-of-central-directory signature not found.  Either this file 
    is not a zipfile, or it constitutes one disk of a multi-part archive.        
  
    In the latter case the central directory and zipfile comment will be
    found on the last disk(s) of this archive. unzip:  cannot find 
    zipfile directory in one of Xcode_8_beta.xip or Xcode_8_beta.xip.zip, 
    and cannot find Xcode_8_beta.xip.ZIP, period.
  </code></pre>