gitlab-ci.yml: syntax check the python scripts

Signed-off-by: Angus Ainslie <angus@akkea.ca>
3 jobs for arts-gps in 3 minutes and 14 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #294657
librem5
build:deb

00:01:14

 
  Test
passed #294658
librem5
test:download:deb

00:01:33

passed #294659
librem5
test:download:pip

00:01:58