title: JupyterLab plotly extension error: Cannot find module jupyter\lab\staging\node_modules\ejs\postinstall.js
body: <p>I am trying to install JupyterLab renderer support for Plotly using:</p>
  <pre><code>jupyter labextension install jupyterlab-plotly@4.10.0
  </code></pre>
  <p>and I get</p>
  <blockquote>
  <p>RuntimeError: npm dependencies failed to install</p>
  </blockquote>
  <p>The log file contains the following:</p>
  <pre><code>[LabBuildApp] Building in C:\Users\&lt;user&gt;\anaconda3\share\jupyter\lab
  [LabBuildApp] Node v14.11.0
  
  [LabBuildApp] Yarn configuration loaded.
  [LabBuildApp] Building jupyterlab assets (build:prod:minimize)
  [LabBuildApp] &gt; node C:\Users\&lt;user&gt;\anaconda3\lib\site-packages\jupyterlab\staging\yarn.js install --non-interactive
  [LabBuildApp] yarn install v1.21.1
  [1/5] Validating package.json...
  [2/5] Resolving packages...
  [3/5] Fetching packages...
  info fsevents@2.1.3: The platform &quot;win32&quot; is incompatible with this module.
  info &quot;fsevents@2.1.3&quot; is an optional dependency and failed compatibility check. Excluding it from installation.
  info fsevents@1.2.13: The platform &quot;win32&quot; is incompatible with this module.
  info &quot;fsevents@1.2.13&quot; is an optional dependency and failed compatibility check. Excluding it from installation.
  [4/5] Linking dependencies...
  warning &quot; &gt; @lumino/coreutils@1.5.0&quot; has unmet peer dependency &quot;crypto@1.0.1&quot;.
  [5/5] Building fresh packages...
  error C:\Users\&lt;user&gt;\anaconda3\share\jupyter\lab\staging\node_modules\ejs: Command failed.
  Exit code: 1
  Command: node ./postinstall.js
  Arguments: 
  Directory: C:\Users\&lt;user&gt;\anaconda3\share\jupyter\lab\staging\node_modules\ejs
  Output:
  internal/modules/cjs/loader.js:896
    throw err;
    ^
  
  Error: Cannot find module 'C:\Users\&lt;user&gt;\anaconda3\share\jupyter\lab\staging\node_modules\ejs\postinstall.js'
      at Function.Module._resolveFilename (internal/modules/cjs/loader.js:893:15)
      at Function.Module._load (internal/modules/cjs/loader.js:743:27)
      at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
      at internal/main/run_main_module.js:17:47 {
    code: 'MODULE_NOT_FOUND',
    requireStack: []
  }
  info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
  
  [LabBuildApp] npm dependencies failed to install
  [LabBuildApp] Traceback (most recent call last):
  
  [LabBuildApp]   File &quot;C:\Users\&lt;user&gt;\anaconda3\lib\site-packages\jupyterlab\debuglog.py&quot;, line 47, in debug_logging
      yield
  
  [LabBuildApp]   File &quot;C:\Users\&lt;user&gt;\anaconda3\lib\site-packages\jupyterlab\labapp.py&quot;, line 138, in start
      raise e
  
  [LabBuildApp]   File &quot;C:\Users\&lt;user&gt;\anaconda3\lib\site-packages\jupyterlab\labapp.py&quot;, line 134, in start
      build(name=self.name, version=self.version,
  
  [LabBuildApp]   File &quot;C:\Users\&lt;user&gt;\anaconda3\lib\site-packages\jupyterlab\commands.py&quot;, line 459, in build
      return handler.build(name=name, version=version, static_url=static_url,
  
  [LabBuildApp]   File &quot;C:\Users\&lt;user&gt;\anaconda3\lib\site-packages\jupyterlab\commands.py&quot;, line 652, in build
      raise RuntimeError(msg)
  
  [LabBuildApp] RuntimeError: npm dependencies failed to install
  
  [LabBuildApp] Exiting application: JupyterLab
  </code></pre>
  <p>When I open JupyterLab I am asked to do a</p>
  <pre><code>jupyter lab build
  </code></pre>
  <p>After my attempt, I get the same error in the logfile.</p>
  <p>I am using Windows10, node.js 14.11.0 (installed using conda), JupyterLab 2.1.5</p>
  <p>Note that I have tried:</p>
  <ul>
  <li>uninstalling conda's node.js and installing node.js directly from node-v12.18.3-x64.msi</li>
  <li>uninstalling and installing Anaconda</li>
  </ul>
  <p>both with no luck.</p>