python: add tox support

This is intended to be a manually run, non-CI script.

Use tox to test the linters against all python versions from 3.6 to
3.10. This will only work if you actually have those versions installed
locally, but Fedora makes this easy:

> sudo dnf install python3.6 python3.7 python3.8 python3.9 python3.10

Unlike the pipenv tests (make venv-check), this pulls "whichever"
versions of the python packages, so they are unpinned and may break as
time goes on. In the case that breakages are found, setup.cfg should be
amended accordingly to avoid the bad dependant versions, or the code
should be amended to work around the issue.

With confidence that the tests pass on 3.6 through 3.10 inclusive, add
the appropriate classifiers to setup.cfg to indicate which versions we
claim to support.

Tox 3.18.0 or above is required to use the 'allowlist_externals' option.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Tested-by: Cleber Rosa <crosa@redhat.com>
Message-id: 20210527211715.394144-31-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/.gitignore

@@ -13,3 +13,4 @@ qemu.egg-info/
 
 # virtual environments (pipenv et al)
 .venv/
+.tox/

python/Makefile

@@ -16,6 +16,8 @@ help:
 	@echo ""
 	@echo "make check:      run linters using the current environment."
 	@echo ""
+	@echo "make check-tox:  run linters using multiple python versions."
+	@echo ""
 	@echo "make clean:      remove package build output."
 	@echo ""
 	@echo "make distclean:  remove venv files, qemu package forwarder,"
@@ -36,8 +38,11 @@ develop:
 check:
 	@avocado --config avocado.cfg run tests/
 
+check-tox:
+	@tox
+
 clean:
 	python3 setup.py clean --all
 
 distclean: clean
-	rm -rf qemu.egg-info/ .venv/ dist/
+	rm -rf qemu.egg-info/ .venv/ .tox/ dist/

python/setup.cfg

@@ -14,6 +14,11 @@ classifiers =
     Natural Language :: English
     Operating System :: OS Independent
     Programming Language :: Python :: 3 :: Only
+    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
 
 [options]
 python_requires = >= 3.6
@@ -30,12 +35,13 @@ devel =
     isort >= 5.1.2
     mypy >= 0.770
     pylint >= 2.8.0
-
+    tox >= 3.18.0
 
 [flake8]
 extend-ignore = E722  # Prefer pylint's bare-except checks to flake8's
 exclude = __pycache__,
           .venv,
+          .tox,
 
 [mypy]
 strict = True
@@ -79,3 +85,18 @@ include_trailing_comma=True
 line_length=72
 lines_after_imports=2
 multi_line_output=3
+
+# tox (https://tox.readthedocs.io/) is a tool for running tests in
+# multiple virtualenvs. This configuration file will run the test suite
+# on all supported python versions. To use it, "pip install tox" and
+# then run "tox" from this directory. You will need all of these versions
+# of python available on your system to run this test.
+
+[tox:tox]
+envlist = py36, py37, py38, py39, py310
+
+[testenv]
+allowlist_externals = make
+deps = .[devel]
+commands =
+    make check