title: Nuget Package - feed (VSTS) :Exception 'System.AggregateException' thrown when trying to add source
body: <p>I have created a new feed with in Package Release hub (VSTS), installed the credentials, then added the package source. </p>
  
  <p>Now, I am using Visual Studio 2015 to install Micrososft.Aspnet.mvc to a project, however it gives the following error:</p>
  
  <pre><code>Exception 'System.AggregateException' thrown when trying to add source
  'https://mysite.pkgs.visualstudio.com/DefaultCollection/_packaging/MyLogUtils/nuget/v3/index.json'.
  Please verify all your online package sources are available.    
  </code></pre>
  
  <p>I need to install NuGet packages normally, so I removed the feed from VSTS. However, the problem persists. How can this problem be resolved?</p>