ci: enable PDF documentation builds

.gitlab-ci.yml

@@ -63,6 +63,17 @@ build documentation:
       - doc/build/html/
     expire_in: 1 month
 
+build PDF documentation:
+  stage: test
+  script:
+    - pip3 install sympy
+    - make -C doc latex SPHINXOPTS='-n -W'
+    - cd doc/build/latex
+    - make all-pdf
+  artifacts:
+    paths:
+      - doc/build/latex/kwant.pdf
+    expire_in: 1 month
 
 run tests:
   stage: test