title: User [X] does not have permission to access user [X:importSshPublicKey]
body: <p>I'm trying to run <code>cloud compute os-login ssh-keys add</code>:
  I get </p>
  
  <pre><code>ERROR: (gcloud.compute.os-login.ssh-keys.add) 
  User [X] does not have permission to access user [X:importSshPublicKey] (or it may not exist): 
  Insufficient IAM permissions. 
  The instance belongs to an external organization. 
  You must be granted the roles/compute.osLoginExternalUser IAM role 
  on the external organization to configure POSIX account information.
  </code></pre>
  
  <p>where X is the same user in both cases. How to add the permissions I need via the <code>gcloud</code> command line?</p>