Remove support for unsupported Python/Django combinations. (#48)

* Remove support for unsupported Python/Django combinations.

* Run GitHub actions on pull requests.

* Use Python3.9 for docs and linting.

* Remove max_parallel setting for GitHub Actions to speed up test runs.

Author: YPCrumble

.github/workflows/python.yml

@@ -3,15 +3,14 @@
 
 name: Python
 
-on: [push]
+on: [push, pull_request]
 
 jobs:
   build:
     runs-on: ubuntu-latest
     strategy:
-      max-parallel: 4
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8, "pypy3"]
+        python-version: [3.5, 3.6, 3.7, 3.8, 3.9, "pypy3"]
 
     steps:
       - uses: actions/checkout@v2

tox.ini

@@ -1,20 +1,22 @@
 [tox]
 envlist =
-    lint-py36,
-    readme-py36,
-    docs-py36,
-    py35-django{111,20,21,22},
-    py36-django{111,20,21,22,30},
-    py37-django{111,20,21,22,30},
-    py38-django{22,30},
-    pypy3-django{111,20,21,22},
+    lint-py39,
+    readme-py39,
+    docs-py39,
+    py35-django{22},
+    py36-django{22,31},
+    py37-django{22,31},
+    py38-django{22,31},
+    py39-django{22,31},
+    pypy3-django{22,31},
 
 [gh-actions]
 python =
   3.5: py35
   3.6: py36
   3.7: py37
-  3.8: py38, lint, restlint
+  3.8: py38
+  3.9: py39, lint, restlint
   pypy3: pypy3
 
 [testenv]
@@ -24,28 +26,25 @@ setenv =
     PYTHONPATH = {toxinidir}
 deps =
     -rtests/requirements.txt
-    django111: Django >=1.11, <2.0
-    django20: Django>=2.0,<2.1
-    django21: Django>=2.1,<2.2
     django22: Django>=2.2,<3
-    django30: Django>=3.0
+    django31: Django>=3.1,<3.2
 commands =
     pytest {posargs:tests}
 
-[testenv:docs-py36]
+[testenv:docs-py39]
 deps =
     sphinx
 commands =
     docs: sphinx-build -b html -d {envtmpdir}/doctrees docs {envtmpdir}/html
 
-[testenv:readme-py36]
+[testenv:readme-py39]
 deps =
     twine
     readme_renderer[md]
 commands =
     python setup.py sdist
     twine check dist/*
 
-[testenv:lint-py36]
+[testenv:lint-py39]
 extras = dev
 commands=therapist run --use-tracked-files