Drupal Console is sunsetted
A couple of months ago Drupal Console was declared end of life.
Launched at the same time as Drupal 8 back in 2016, Drupal Console was installed via composer. e.g.
composer require-dev drupal/console:~1.0 --pr
Trying that with a stable Drupal 8 site you may run into problems. e.g.
Your requirements could not be resolved to an installable set of packages.