Comment 6 for bug 1643737

Also, re-reading this revealed the bug has slightly changed:

Note this time around, the password seems to re-appear in the GUI after being entered - however, it's not stored in the conf file, and I'm promoted to enter it upon reboot, so it's now:

  - storing it somewhere (maybe somewhere preferrable to a globally readable file!)
  - and then not using it upon reboot.

After entering it in the conf file, it started working again, upon reboot.

Note that this version has been updated to:

root@stuart:/etc/pam.d# apt list network-manager
Listing... Done
network-manager/xenial-updates,now 1.2.2-0ubuntu0.16.04.3 amd64 [installed,automatic]

So it's getting better, but not there yet.