Update .gitlab-ci.yml

1 job for master in 16 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #97
pages
build

00:00:16

 
Name Stage Failure
failed
build Test There is an unknown failure, please try again
(running on Debian, switching to user mode!)
tlmgr: package repository http://mirrors.ircam.fr/pub/CTAN/systems/texlive/tlnet (verified)
[1/1, ??:??/??:??] install: babel-french [15k]
tlmgr: package log updated: /root/texmf/web2c/tlmgr.log
running mktexlsr ...
done running mktexlsr.
$ latexmk -f -xelatex main.tex
/bin/bash: line 55: latexmk: command not found
ERROR: Job failed: exit code 1