Run unittests in tox against many Pythons

Author: etingof

tox.ini

@@ -1,23 +1,49 @@
 [tox]
 minversion = 3.4.0
-envlist = unittest, flake8, docs, bandit, build
+skip_missing_interpreters = true
+envlist =
+    {py27, py35, py36, py37, py38}-{unittest},
+    cover, docs, bandit, build
 
 [testenv]
-basepython = python3
 usedevelop = True
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning
-install_command = pip install {opts} {packages}
+deps = pip >= 19.3.1
+install_command =
+    pip install {opts} {packages}
 
 [testenv:unittest]
 deps =
-  discover
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt
-commands = discover -s tests
+    discover
+    -r{toxinidir}/test-requirements.txt
+    -r{toxinidir}/requirements.txt
+commands =
+    discover -s tests
+
+[testenv:py27-unittest]
+deps = {[testenv:unittest]deps}
+commands = {[testenv:unittest]commands}
+
+[testenv:py35-unittest]
+deps = {[testenv:unittest]deps}
+commands = {[testenv:unittest]commands}
+
+[testenv:py36-unittest]
+deps = {[testenv:unittest]deps}
+commands = {[testenv:unittest]commands}
+
+[testenv:py37-unittest]
+deps = {[testenv:unittest]deps}
+commands = {[testenv:unittest]commands}
+
+[testenv:py38-unittest]
+deps = {[testenv:unittest]deps}
+commands = {[testenv:unittest]commands}
 
 [testenv:flake8]
+basepython=python3
 skip_install = true
 deps =
     flake8
@@ -31,6 +57,7 @@ commands =
     flake8 --config .flake8.ini --count --import-order-style pep8 --application-import-names apacheconfig apacheconfig tests {posargs}
 
 [testenv:pylint]
+basepython=python3
 deps =
     pyflakes
     pylint
@@ -39,6 +66,7 @@ commands =
     pylint apacheconfig
 
 [testenv:cover]
+basepython=python3
 setenv =
    {[testenv]setenv}
    PYTHON=coverage run --parallel-mode
@@ -50,17 +78,21 @@ commands = coverage erase
            coverage report --fail-under 80
 
 [testenv:bandit]
+basepython=python3
 skip_install = true
 deps =
     bandit
 commands =
     bandit -r apacheconfig -c .bandit.yml
 
 [testenv:docs]
+basepython=python3
 skip_install = true
+whitelist_externals = make
 commands = make -C docs html
 
 [testenv:build]
+basepython=python3
 skip_install = true
 deps =
     wheel