Path to translation files is hardcoded in the install

Problem/Motivation

function install_check_translations($langcode, $server_pattern) {
  $requirements = array();

  $readable = FALSE;
  $writable = FALSE;
  // @todo: Make this configurable.
  $site_path = \Drupal::service('site.path');
  $files_directory =  $site_path . '/files';
  $translations_directory = $site_path . '/files/translations';

Proposed resolution

I couldn't find the TODO, so this will have to be it.
#1658842: Introduce a translations:// stream wrapper to access the .po file directory → makes this a lot easier.

Remaining tasks

Do it. Make the path configurable.

User interface changes

API changes

Data model changes