Add Gitlab stage for Python 3.7 because it is Debian default version

.gitlab-ci.yml

@@ -2,12 +2,19 @@ stages:
   - test
   - quality-assurance
 
+py37:
+  stage: test
+  image: python:3.7-alpine
+  before_script:
+    - pip install tox
+  script: tox -e py3
+
 py38:
   stage: test
   image: python:3.8-alpine
   before_script:
     - pip install tox
-  script: tox -e py38
+  script: tox -e py3
 
 
 py39:
@@ -15,7 +22,7 @@ py39:
   image: python:3.9-alpine
   before_script:
     - pip install tox
-  script: tox -e py39
+  script: tox -e py3
 
 linters:
   stage: quality-assurance

tox.ini

@@ -1,7 +1,6 @@
 [tox]
 envlist =
-    py38
-    py39
+    py3
     linters
 
 skipsdist = True