Update tox.ini to test on Python 3.9 and 3.10

Author: domdfcoding

tox.ini

@@ -8,7 +8,7 @@
 # for testing and it is disabled by default.
 
 [tox]
-envlist = lint, py27, py35, py36, py37, py38
+envlist = lint, py27, py35, py36, py37, py38, py39, py310
 
 [testenv]
 commands = pytest -v --doctest-modules --ignore benchmark.py
@@ -97,6 +97,40 @@ deps =
     pandas
     wcwidth
 
+
+[testenv:py39]
+basepython = python3.9
+commands = pytest -v --doctest-modules --ignore benchmark.py
+deps =
+    pytest
+
+[testenv:py39-extra]
+basepython = python3.9
+commands = pytest -v --doctest-modules --ignore benchmark.py
+deps =
+    pytest
+    numpy
+    pandas
+    wcwidth
+
+
+[testenv:py310]
+basepython = python3.10
+commands = pytest -v --doctest-modules --ignore benchmark.py
+deps =
+    pytest
+
+[testenv:py310-extra]
+basepython = python3.10
+setenv = PYTHONDEVMODE = 1
+commands = pytest -v --doctest-modules --ignore benchmark.py
+deps =
+    pytest
+    numpy
+    pandas
+    wcwidth
+
+
 [flake8]
 max-complexity = 22
 max-line-length = 99