CI related tweaks

.gitlab-ci.yml

 image: dockershelf/latex:full
 
-before_script:
-    - apt-get install -qy python3-pygments
-
 build:
     script:
     - cd spec

spec/highlight.py

-#! /usr/bin/env python
+#! /usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # This is a thin wraper arround pygmentize that adds support for SMT-LIB/Alethe.