Drop Python 3.6 support and add 3.11 support.

Python 3.6 is now EoL and testing it is not tractable anymore. This
commit removes support (marked via package metadata trove classifiers)
and CI configuration for running with 3.6 from the project.

.github/workflows/main.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9, "3.10"]
+        python-version: [3.7, 3.8, 3.9, "3.10", "3.11"]
         os: ["macOS-latest", "ubuntu-latest", "windows-latest"]
     steps:
       - uses: actions/checkout@v2

setup.cfg

@@ -15,11 +15,11 @@ classifier =
     Operating System :: OS Independent
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
+    Programming Language :: Python :: 3.11
     Topic :: Software Development :: Testing
     Topic :: Software Development :: Quality Assurance
 project_urls =

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = py310,py39,py38,py37,py36,pep8
+envlist = py311,py310,py39,py38,py37,pep8
 skipsdist = True
 
 [testenv]