I have Ubuntu 15.10 and I refused by accident the 16.04 LTS upgrade. So, now when I launch
do-release-upgrade, no new release where found and I cannot upgrade to 16.04 LTS.
I have also checked the content of the file
New release '16.04.1 LTS' available. Run 'do-release-upgrade' to upgrade to it.
Is there a way to re-enable Ubuntu upgrade somewhere?