system_init() calls path_is_admin() for cli requests

system_init() has been removed in 8.x, and assets are added in a hook that only runs for HTML page requests.

We can't make that change for 7.x I think, however I just ran into an issue where hook_admin_paths() in a custom module was checking a class that had moved in an update, and this was resulting in fatal errors when running drush updb.

There's absolutely no reason to execute that code for any full bootstrap, so I think it's reasonable to add a drupal_is_cli() check there.