sync .gitlab-ci.yml with master

This is done instead of picking all changes that were commited to master
and not reflected in stable.

Current master revision is 8a6d320b.
22 jobs for test-stable-ci-fix in 7 minutes and 47 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build Env
manual build-env:conda #210167
allowed to fail manual
manual build-env:debian #210166
allowed to fail manual
manual build-env:default #210168
allowed to fail manual
manual build-env:ubuntu #210165
allowed to fail manual
 
  Build
passed build:debian #210170

00:02:20

passed build:latest #210173

00:01:49

passed build:no-extras #210172

00:02:11

passed build:stable #210171

00:02:20

passed build:ubuntu #210169

00:02:51

 
  Test
passed build PDF documentation #210182

00:04:27

passed build documentation #210181

00:04:14

failed check for broken links in doc #210183
allowed to fail

00:01:05

passed check for dependencies installed #210175

00:00:36

passed check whitespace style #210174

00:00:38

passed test:debian #210179

00:01:44

passed test:latest #210180

00:02:01

passed test:no-extras #210177

00:01:14

passed test:stable #210176

00:02:09

passed test:ubuntu #210178

00:01:45

 
  Deploy
manual remove_coverage #210184
allowed to fail manual
manual remove_docs #210186
allowed to fail manual
passed upload documentation to the test server #210185

00:00:25

 
Name Stage Failure
failed
check for broken links in doc Test
writing output... [100%] tutorial/superconductors


build finished with problems, 156 warnings.
Makefile:119: recipe for target 'linkcheck' failed
make: Leaving directory '/builds/kwant/kwant/doc'
make: *** [linkcheck] Error 1
Authenticating with credentials from /root/.docker/config.json
ERROR: Job failed: exit code 1