Update uuid check

.gitlab-ci.yml

@@ -5,8 +5,7 @@ deploy:
         paths:
             - vendor/
     script:
-        - pip install -r requirements.txt
-        - python check_uniqueness_of_uids.py
+        - python3 check_uniqueness_of_uids.py
         - env LANG=en_US.UTF-8 bundle install --path=vendor/
         - env LANG=en_US.UTF-8 bundle exec jekyll build
         - rsync -6av --delete-after _site/ /var/www/html/

check_uniqueness_of_uids.py

+# requires python-frontmatter==1.0.0
+
 import frontmatter
 import glob
 import sys

requirements.txt

-python-frontmatter==1.0.0