title: VSTS build agent can't download VSTS private packages
body: <p>I am trying to add a build definition for a project that has private nuget packages hosted in VSTS. The local build works just fine but when I try to build it with an on premise build agent I get the following error:
  <a href="https://i.stack.imgur.com/L239m.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/L239m.png" alt="enter image description here"></a></p>
  
  <p>The agent runs behind a proxy and in the build definition i have the following settings:</p>
  
  <p><a href="https://i.stack.imgur.com/ow6al.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ow6al.png" alt="enter image description here"></a></p>
  
  <p>This is driving me mad please HELP !</p>