Bump python and postrgres in CI

.gitlab-ci.yml

@@ -1,4 +1,4 @@
-image: "python:3.5"
+image: "python:3.7"
 
 variables:
     # GestioCOF settings
@@ -18,7 +18,8 @@ variables:
     # psql password authentication
     PGPASSWORD: $POSTGRES_PASSWORD
 
-.test_template:
+test:
+    stage: test
     before_script:
         - mkdir -p vendor/{pip,apt}
         - apt-get update -q && apt-get -o dir::cache::archives="vendor/apt" install -yqq postgresql-client
@@ -33,7 +34,7 @@ variables:
     after_script:
         - coverage report
     services:
-        - postgres:9.6
+        - postgres:11.7
         - redis:latest
     cache:
         key: test
@@ -43,18 +44,7 @@ variables:
     # 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
     before_script:
         - mkdir -p vendor/pip
@@ -81,7 +71,7 @@ migration_checks:
     script: python manage.py makemigrations --dry-run --check
     services:
         # this should not be necessary…
-        - postgres:9.6
+        - postgres:11.7
     cache:
         key: migration_checks
         paths: