title: npm install from tfs feed (on build process) give error: Unable to authenticate
body: <p>We have our own npm package and a project that uses it,
  I want to publish it to a tfs feed - repository and install it from there instead of from a physical file.</p>
  
  <p>I published the package to the feed from my development machine,<br>
  and I changed the reference within the project that consumes it. </p>
  
  <p>The whole process works fine from my machine, but when I try to consume the package on a build process in the tfs - it fails with the error :</p>
  
  <blockquote>
    <p>Unable to authenticate, your authentication token seems to be invalid.</p>
  </blockquote>
  
  <p>I've created <code>.npmrc</code> file at the project level with the registry address, and another file with credentials on the user directory,   and I did the same on the TFS machine.</p>
  
  <p>What can cause the npm install (from my feed) to not work on the tfs machine?</p>
  
  <p><strong>EDIT:</strong><br>
  When I add prefix @my to the registry at the user-level .npmrc file - like this:</p>
  
  <pre><code>@my:registry=https://my-feed-address
  </code></pre>
  
  <p>The error changes to:
  "No valid versions available for my-package"</p>