Revert "Disable the pylint CI test until upstream's bug is fixed"

This reverts commit 791d44f1b9.

.gitlab-ci.yml

@@ -77,6 +77,19 @@ pytest-latest:
     - python3 setup.py install
     - py.test -v test/
 
+pylint-latest:
+  stage: test
+  image: python:3
+  script:
+    - apt-get update && apt-get install -y libidn11-dev
+    - git clone git://git.louiz.org/slixmpp
+    - pip3 install pylint pyasn1-modules cffi --upgrade
+    - cd slixmpp
+    - python3 setup.py install
+    - cd ..
+    - python3 setup.py install
+    - pylint -E poezio
+
 pylint-plugins:
   stage: test
   image: python:3