CI: bring back py36

.gitlab-ci.yml

@@ -156,6 +156,10 @@ variables:
   script:
     - bash ./.ci/test_template.sh
 
+test:3.6:
+  stage: test
+  image: pauldmccarthy/fsleyes-py36-wxpy4-gtk3
+  <<: *test_template
 
 test:3.7:
   stage: test