add natsort as dep

.gitlab-ci.yml

@@ -17,6 +17,8 @@ prepare:index:
   rules:
     - if: $CI_COMMIT_REF_NAME
     - if: '$CI_PIPELINE_SOURCE == "merge_request_event" && $CI_COMMIT_MESSAGE !~ /tmpBranch/ && $CI_COMMIT_MESSAGE !~ /Update index/'
+  before_script:
+    - pip install natsort
   script:
     - python .ci/generateIndex.py
     - mkdir .tmp