Run CI against 3.9 pre-release (#664)

Author: hynek

.github/workflows/main.yml

@@ -13,11 +13,11 @@ jobs:
     name: "Python ${{ matrix.python-version }}"
     runs-on: "ubuntu-latest"
     env:
-      USING_COVERAGE: '2.7,3.7,3.8'
+      USING_COVERAGE: "2.7,3.7,3.8"
 
     strategy:
       matrix:
-        python-version: ["2.7", "3.5", "3.6", "3.7", "3.8", "pypy2", "pypy3"]
+        python-version: ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9.0-alpha - 3.9.0", "pypy2", "pypy3"]
 
     steps:
       - uses: "actions/checkout@v2"

tox.ini

@@ -14,12 +14,13 @@ python =
     3.6: py36
     3.7: py37, docs
     3.8: py38, lint, manifest, typing, changelog
+    3.9: py39
     pypy2: pypy2
     pypy3: pypy3
 
 
 [tox]
-envlist = typing,lint,py27,py35,py36,py37,py38,pypy,pypy3,manifest,docs,pypi-description,changelog,coverage-report
+envlist = typing,lint,py27,py35,py36,py37,py38,py39,pypy,pypy3,manifest,docs,pypi-description,changelog,coverage-report
 isolated_build = True