build: Add basic testing via tox

For now, only test PEP 8 compliance with flake8 (in the flake8
testenv), and test installing and enabling the plugin in a Tutor
environment (in the default testenv, to be invoked as "py38", "py39"
etc.)

.gitignore

@@ -3,6 +3,10 @@
 TODO
 __pycache__
 *.egg-info/
+.eggs/
 /build/
 /dist/
-.idea
+.idea
+.python-version
+.tox
+tests/tutor-sandbox/config.yml

setup.py

@@ -16,7 +16,7 @@ def load_readme():
     url="https://github.com/hastexo/tutor-contrib-retirement",
     project_urls={
         "Code": "https://github.com/hastexo/tutor-contrib-retirement",
-        "Issue tracker": "https://github.com/hastexo/tutor-contrib-retirement/issues",
+        "Issue tracker": "https://github.com/hastexo/tutor-contrib-retirement/issues",  # noqa: E501
     },
     license="AGPLv3",
     author="hastexo",

tests/tutor-sandbox/.placeholder

@@ -0,0 +1,2 @@
+This directory serves as a sandbox for Tutor configurations generated
+in the course of automated testing.

tox.ini

@@ -0,0 +1,25 @@
+[tox]
+envlist = py{38,39},flake8
+
+[gh-actions]
+python =
+    3.8: py38,flake8
+    3.9: py39,flake8
+
+[flake8]
+ignore = E124,W504
+exclude = .svn,CVS,.bzr,.hg,.git,__pycache__,.tox,.eggs,*.egg,src
+
+[testenv]
+setenv =
+  TUTOR_ROOT = tests/tutor-sandbox
+# No "deps" list is necessary here, since setup.py has tutor in its
+# install_requires list.
+commands =
+  tutor plugins enable retirement
+  tutor plugins list
+
+[testenv:flake8]
+skip_install = True
+deps = flake8
+commands = flake8

tutorretirement/__about__.py

@@ -6,4 +6,4 @@
 # options) by:
 # https://packaging.python.org/guides/single-sourcing-package-version/
 __version__ = pkg_resources.get_distribution(
-    'tutor-contrib-webhook-receiver').version
+    'tutor-contrib-retirement').version

tutorretirement/plugin.py

@@ -2,7 +2,6 @@
 import os
 import pkg_resources
 
-from .__about__ import __version__
 
 templates = pkg_resources.resource_filename(
     "tutorretirement", "templates"