title: The diagnostic tools failed unexpectly in Visual Studio 2015
body: <p>In the diagnostics hub output window, I can see the line</p>
  
  <pre><code>Unexpected character encountered while parsing value: &lt;. Path '', line 0, position 0.
  </code></pre>
  
  <p>for one or more times.</p>
  
  <p>Can anyone give me a hint where to look for this "unexpected character"?</p>