Update tox configuration in setup.cfg to run tests on Python 3.10

Author: althonos

setup.cfg

@@ -130,7 +130,7 @@ markers =
 # --- Tox automation configuration ---------------------------------------------
 
 [tox:tox]
-envlist = py{27,34}{,-scandir}, py{35,36,37,38,39}, pypy{27,36,37}, typecheck, codestyle, docstyle, codeformat
+envlist = py{27,34}{,-scandir}, py{35,36,37,38,39,310}, pypy{27,36,37}, typecheck, codestyle, docstyle, codeformat
 sitepackages = false
 skip_missing_interpreters = true
 requires =
@@ -141,9 +141,9 @@ commands = python -m coverage run --rcfile {toxinidir}/setup.cfg -m pytest {posa
 deps =
   -rtests/requirements.txt
   coverage~=5.0
-  py{35,36,37,38,39,py36,py37}: pytest~=6.0
+  py{35,36,37,38,39,310,py36,py37}: pytest~=6.0
   py{27,34,py27}: pytest~=4.6
-  py{35,36,37,38,39,py36,py37}: pytest-randomly~=3.5
+  py{35,36,37,38,39,310,py36,py37}: pytest-randomly~=3.5
   py{27,34,py27}: pytest-randomly~=1.2
   scandir: .[scandir]
   !scandir: .
@@ -183,6 +183,7 @@ python =
     3.7: py37
     3.8: py38
     3.9: py39
+    3.10: py310
     pypy-2.7: pypy27
     pypy-3.6: pypy36
     pypy-3.7: pypy37