title: JupyterLab : cannot save notebook. "File > save notebook" greyed out. Auto save and Cmd + S also doesn't work
body: <p>JupyterLab is in a <a href="https://cloud.google.com/deep-learning-vm/" rel="nofollow noreferrer">gcp Deep learning vm</a>. </p>
  
  <p>Since few hours ago I can't save any changes in JupyterLab.</p>
  
  <p>There are unsaved changes.</p>
  
  <p><a href="https://i.stack.imgur.com/hJ0Hw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hJ0Hw.png" alt="enter image description here"></a></p>
  
  <p>save notebook greyed out.</p>
  
  <p><a href="https://i.stack.imgur.com/mXOTe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/mXOTe.png" alt="enter image description here"></a></p>
  
  <p>Also, if I try to delete a file from the left pane, it gives a 500 error.</p>
  
  <p><a href="https://i.stack.imgur.com/4F7DH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4F7DH.png" alt="enter image description here"></a></p>
  
  <p>The only change I recall making prior to this breaking is this. I had this error when I tried to do git operations in the command line.</p>
  
  <pre><code>Another git process seems to be running in this repository, e.g.
  an editor opened by 'git commit'. Please make sure all processes
  are terminated then try again. If it still fails, a git process
  may have crashed in this repository earlier:
  </code></pre>
  
  <p>Therefore I did this</p>
  
  <pre><code>rm -f ./.git/index.lock
  </code></pre>
  
  <p>And the git command worked correctly. This the only thing I recall doing prior to this error.</p>
  
  <p>Afterwards, I deleted the repository and recloned it.</p>
  
  <p>And since I had to type sudo everytime I had the user claim the jupyter directory. But this error was there before I made this change.</p>
  
  <pre><code>udo chown your_username directory
  </code></pre>