title: npm install of private package fails when package has public dependencies
body: <p>Lets say I have a private npm repository, hosted within <a href="https://www.jfrog.com/confluence/display/RTF/Welcome+to+Artifactory" rel="noreferrer">JFrog artifactory</a>: 
   <code>https://my-domain.com/artifactory/api/npm/my-repo</code>.
  In this repository I published one npm package: <code>my-package</code>, which builds fine. <code>my-package</code> has a dependency (or more) to public npm <a href="https://registry.npmjs.org" rel="noreferrer">packages </a> e.g. <code>lodash</code>.</p>
  
  <p>However, when I create a new project and attempt to install <code>my-package</code> I get the following error:</p>
  
  <pre class="lang-sh prettyprint-override"><code>$ npm install my-package --registry https://my-domain.com/artifactory/api/npm/my-repo
  npm ERR! code E404
  npm ERR! 404 Not Found - GET https://my-domain.com/artifactory/api/npm/my-repo/lodash - not_found
  npm ERR! 404
  npm ERR! 404  'lodash^4.17.11' is not in the npm registry.
  npm ERR! 404 You should bug the author to publish it (or use the name yourself!)
  npm ERR! 404 It was specified as a dependency of 'my-package'
  npm ERR! 404
  npm ERR! 404 Note that you can also install from a
  npm ERR! 404 tarball, folder, http url, or git url.
  
  npm ERR! A complete log of this run can be found in:
  npm ERR!     C:\Users\&lt;username&gt;\AppData\Roaming\npm-cache\_logs\2019-04-29T12_47_51_647Z-debug.log
  </code></pre>
  
  <p>It appears as though <code>npm</code> is searching within my private repository for all the dependencies <code>my-package</code> requires when I specify the <code>--registry</code> option when running an <code>npm install</code>. However, <code>my-package</code> is dependent upon public dependencies, which are not in my private registry.</p>
  
  <p><strong>My Question</strong></p>
  
  <p>How to install an npm package from a private registry that has public dependencies? Perhaps this is also just a JFrog issue?</p>
  
  <p>Any help would be greatly appreciated!</p>