Run test on Python 3.7

Hugo Osvaldo Barrera · Hugo Osvaldo Barrera · commit 7a7deffa2cbf · 2021-08-07T17:23:10.000+02:00
Run these on a synthetic environment, since no distribution seems to
currently ship this version.
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
@@ -0,0 +1,6 @@
+python37:
+  image: python:3.7
+  before_script:
+    - make -e install-dev
+  script:
+    - make -e ci-test
