title: Xcode 9.3 and update to High Sierra: Instruments can't open *.tracetemplate files even after full reinstall
body: <p>With the last update of Xcode to 9.3 running on High Sierra, I realized that <code>Instruments</code> is not working any more. </p>
  
  <p>When I try to open it from inside Xcode using <code>Open Developer Tool &gt; Instruments</code>, I can see the template chooser dialog but as soon I pick one, a dialog appears:</p>
  
  <pre><code>The document "Allocations.tracetemplate" could not be opened. Instruments cannot open files of this type.
  </code></pre>
  
  <p><code>Allocations.tracetemplate</code> could not be handled because Instruments cannot open files of this type.</p>
  
  <p>This happens with all templates.</p>
  
  <p>I already tried to reinstall Xcode completely. Before I deleted all files like described here: <a href="https://stackoverflow.com/questions/31011062/how-to-completely-uninstall-xcode-and-clear-all-settings">How to Completely Uninstall Xcode and Clear All Settings</a></p>
  
  <p>I also tried to use 
  sudo chmod a+rwxt /Library/Caches/com.apple.dt.instruments
  (<a href="https://stackoverflow.com/questions/30882233/xcode-6-3-2-instruments-keep-asking-for-trace-template#comment49806199_30882233">Xcode 6.3.2: Instruments keep asking for trace template?</a>)
  but this file does not exist on my computer. </p>
  
  <p>I also installed Xcode 9.4 beta 1 but that didn't solve the issue either.</p>
  
  <p>I also can't find these template files like Allocations.tracetemplate anywhere on my computer. </p>
  
  <p>Any help would be very appreciated ;-)</p>