Modernise build system

{{cookiecutter.project_slug}}/.gitlab-ci.yml

@@ -19,7 +19,7 @@ stages:
   python -V
   python3 -m venv venv
   source venv/bin/activate
-  pip install -U pip setuptools wheel setuptools_scm
+  pip install -U pip setuptools wheel setuptools_scm packaging
   hash -r
   pip freeze
   make install-dev
@@ -30,22 +30,6 @@ stages:
       reports:
         junit: "reports/junit*.xml"
 
-test-py3.6:
-    image: docker.km3net.de/base/python:3.6
-    stage: test
-    script:
-        - *virtualenv_definition
-        - make test
-    <<: *junit_definition
-
-test-py3.7:
-    image: docker.km3net.de/base/python:3.7
-    stage: test
-    script:
-        - *virtualenv_definition
-        - make test
-    <<: *junit_definition
-
 test-py3.8:
     image: docker.km3net.de/base/python:3.8
     stage: test
@@ -137,9 +121,9 @@ pypi:
     stage: release
     cache: {}
     script:
-        - pip install -U twine wheel setuptools_scm
-        - python setup.py sdist
-        - python setup.py bdist_wheel
+        - pip install -U twine wheel setuptools_scm build
+        - python -m build --sdist
+        - python -m build --wheel
         - twine upload dist/*
     only:
         - tags