CI: run tests on python:3.5 and python:3.7

.gitlab-ci.yml

@@ -18,8 +18,7 @@ variables:
     # psql password authentication
     PGPASSWORD: $POSTGRES_PASSWORD
 
-test:
-    stage: test
+.test_template:
     before_script:
         - mkdir -p vendor/{pip,apt}
         - apt-get update -q && apt-get -o dir::cache::archives="vendor/apt" install -yqq postgresql-client
@@ -44,6 +43,16 @@ test:
     # Keep this disabled for now, as it may kill GitLab...
     # coverage: '/TOTAL.*\s(\d+\.\d+)\%$/'
 
+test35:
+  extends: ".test_template"
+  image: "python:3.5"
+  stage: test
+
+test37:
+  extends: ".test_template"
+  image: "python:3.7"
+  stage: test
+
 linters:
     image: python:3.6
     stage: test