apt error: setting locale failed

This can happen sometimes on fresh minimal/alternate installs or in other situations. The fix is pretty simple. Try these, in the following order, testing after each to see if the situation is fixed:

1. Reconfigure locales

   sudo dpkg-reconfigure locales

   if that doesn’t work

2. Reinstall locale language-pack

   sudo apt-get --reinstall install language-pack-it

   if that doesn’t work,

3. Manually force locale settings (persistent)

   sudo update-locale LC_ALL=it_IT.UTF-8 LANG=it_IT.UTF-8