Add Python 3.10 support

Author: bhrutledge

.github/workflows/main.yml

@@ -23,7 +23,7 @@ jobs:
   test:
     strategy:
       matrix:
-        python: [3.6, 3.7, 3.8, 3.9]
+        python: [3.6, 3.7, 3.8, 3.9, 3.10]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps:

docs/contributing.rst

@@ -112,13 +112,13 @@ To pass options to ``pytest``, e.g. the name of a test, run:
 
    tox -e py -- tests/test_upload.py::test_exception_for_http_status
 
-Twine is continuously tested against Python 3.6, 3.7, 3.8, and 3.9 using
+Twine is continuously tested against supported versions of Python using
 `GitHub Actions`_. To run the tests against a specific version, e.g. Python
-3.6, you will need it installed on your machine. Then, run:
+3.8, you will need it installed on your machine. Then, run:
 
 .. code-block:: bash
 
-   tox -e py36
+   tox -e py38
 
 To run the "integration" tests of uploading to real package indexes, run:
 

setup.cfg

@@ -27,6 +27,7 @@ classifiers =
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     Programming Language :: Python :: Implementation :: CPython
 
 [options]

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 3.3
-envlist = lint,types,py{36,37,38,39},integration,docs
+envlist = lint,types,py{36,37,38,39,310},integration,docs
 isolated_build = True
 
 [testenv]