Pathologic was missing because of a .git folder inside.

[yaffs-website] / web / modules / contrib / slick / slick.services.yml

services:
  slick.manager:
    class: Drupal\slick\SlickManager
    parent: blazy.manager.base

  slick.formatter:
    class: Drupal\slick\SlickFormatter
    parent: blazy.formatter.manager

  slick.admin:
    class: Drupal\slick\Form\SlickAdmin
    arguments: ['@blazy.admin.extended', '@slick.manager']