Bug: Neubot repos disabled after Ubuntu distribution upgrade
Before version 0.4.4, Neubot was buggy with respect to Ubuntu distribution upgrade. In particular, it was not able to auto reenable its repository after the upgrade. As a result, the system was no longer able to pull Neubot updates. So, I advise all Ubuntu users to check their version of Neubot and, if it's lower than 0.4.4, manually download and install the latest package, which contains the fix for that bug.
Thanks to Daniel Howard for reminding me I've not widely announced the issue and the fix.