add test for 3.7 and 3.8

.gitlab-ci.yml

@@ -41,6 +41,32 @@ stages:
 variables:
   PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
 
+install_and_test_37:
+  image: python:3.7
+  stage: test
+  script:
+    - pip3 install -e . --no-deps
+    - python3 -m pytest
+  artifacts:
+    when: always
+    untracked: true
+    paths:
+      - build
+    expire_in: 8d
+
+install_and_test_38:
+  image: python:3.8
+  stage: test
+  script:
+    - pip3 install -e . --no-deps
+    - python3 -m pytest
+  artifacts:
+    when: always
+    untracked: true
+    paths:
+      - build
+    expire_in: 8d
+
 install_and_test_39:
   image: python:3.9
   stage: test