'sorry ubuntu 16.04 has experienced an internal error.'

Reading package lists... Done
Building dependency tree
Reading state information... Done
Package gdebi is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
N: Ignoring file '50unattended-upgrades.ucf-dist' in directory '/etc/apt/apt.conf.d/' as it has an invalid filename extension
E: Package 'gdebi' has no installation candidate