title: Can't install any jupyterlab extensions in docker image
body: <p>I am running docker build task in Azure pipelines on a pipeline agent that runs on an on-prem host. I am trying to &quot;RUN jupyter labextension install @jupyter-widgets/jupyterlab-manager&quot;.</p>
  <p>In the base image:
  <code>node=14.14.0</code>
  <code>jupyter=1.0.0</code>
  <code>jupyter-packaging = 0.7.12</code>
  <code>jupyter-resource-usage= 0.5.1</code>
  <code>jupyter_client = 6.1.7</code>
  <code>jupyter_console = 6.2.0</code>
  <code>jupyter_core = 4.7.0</code>
  <code>jupyter_server = 1.6.1</code>
  <code>jupyter_telemetry = 0.1.0</code>
  <code>jupyterhub = 1.3.0</code>
  <code>jupyterhub-base = 1.3.0</code>
  <code>jupyterlab = 3.0.12</code>
  <code>jupyterlab-git = 0.30.0b2</code>
  <code>jupyterlab-templates = 0.2.5</code>
  <code>jupyterlab_code_formatter=1.4.5</code>
  <code>jupyterlab_pygments = 0.1.2</code>
  <code>jupyterlab_server = 2.3.0</code></p>
  <p>Dockerfile looks like this:</p>
  <pre><code>USER root
  COPY files/.npmrc $HOME/.npmrc
  RUN jupyter labextension install --no-build @jupyter-widgets/jupyterlab-manager .....
  </code></pre>
  <p>.npmrc looks like so:</p>
  <pre><code>always-auth=true
  strict-ssl=false
  registry=https://pkgs.dev.azure.com/org-name/proj-name/_packaging/proj-name/npm/registry/
  https-proxy=the-proxy-url
  proxy=the-proxy-url
  </code></pre>
  <p>The pipeline does the following tasks:</p>
  <ol>
  <li>Runs npmAuthenticate task on .npmrc to edit the .npmrc file with the auth-token. This succeeds..</li>
  <li>Next runs docker build. The Dockerfile instructs to copy this modified .npmrc to $HOME and tries to install lab extensions</li>
  </ol>
  <p>Found this thread : <a href="https://github.com/jupyter-widgets/ipywidgets/issues/1982#issuecomment-468716770" rel="nofollow noreferrer">https://github.com/jupyter-widgets/ipywidgets/issues/1982#issuecomment-468716770</a>
  We use jupyterlab v3. So node&gt;=12 is required. So I changed the Dockerfile to:</p>
  <pre><code>USER root
  COPY files/.npmrc $HOME/.npmrc
  RUN conda remove nodejs &amp;&amp; conda install -c conda-forge nodejs=12 &amp;&amp; conda list | grep nodejs &amp;&amp;\
  jupyter labextension install --no-build @jupyter-widgets/jupyterlab-manager .....
  </code></pre>
  <p>Tried this also: <a href="https://stackoverflow.com/a/52484330/3575135">https://stackoverflow.com/a/52484330/3575135</a> . Didnt help</p>
  <p>The normal &quot;npm install @angular/cli&quot; works. But the lab extensions are giving me a hard time. Nothing seems to be working at this point..</p>
  <p>This is the error:</p>
  <p><code>ValueError: &quot;@jupyter-widgets/jupyterlab-manager&quot; is not a valid npm package</code></p>
  <p>Please help!</p>