build: Remove tests/ stub; make make test-all work right (#402)

- The `tests/__init__.py` create/delete thing seems to have been a
  workaround for something that's no longer relevant, so just remove it.
- Same deal for `test_utils/`.
- The `test-all` target needed to depend on `clean` so that `build/lib`
  wouldn't stick around and confuse pytest, and the recipe needed to be
  pruned down to just `tox` because otherwise we'd run the quality checks
  twice. (`quality` is in the tox.ini default env list.)

.gitignore

@@ -69,9 +69,6 @@ docs/edx_django_utils.*.rst
 requirements/private.in
 requirements/private.txt
 
-# tox environment temporary artifacts
-tests/__init__.py
-
 # Development task artifacts
 default.db
 

Makefile

@@ -74,8 +74,7 @@ test: clean ## run tests in the current virtualenv
 diff_cover: test ## find diff lines that need test coverage
 	diff-cover coverage.xml
 
-test-all: ## run tests on every supported Python/Django combination
-	tox -e quality
+test-all: clean ## run quality checks as well as tests on every supported Python/Django combination
 	tox
 
 validate: quality test ## run tests and quality checks

tox.ini

@@ -76,12 +76,10 @@ deps =
     -r{toxinidir}/requirements/quality.txt
      setuptools
 commands =
-    touch tests/__init__.py
-    pylint edx_django_utils tests test_utils manage.py setup.py
-    rm tests/__init__.py
-    pycodestyle edx_django_utils tests manage.py setup.py
-    pydocstyle edx_django_utils tests manage.py setup.py
-    isort --check-only --diff tests test_utils edx_django_utils manage.py setup.py test_settings.py
+    pylint edx_django_utils manage.py setup.py
+    pycodestyle edx_django_utils manage.py setup.py
+    pydocstyle edx_django_utils manage.py setup.py
+    isort --check-only --diff edx_django_utils manage.py setup.py test_settings.py
     make selfcheck
 
 [testenv:isort]
@@ -90,4 +88,4 @@ allowlist_externals =
 deps =
     -r{toxinidir}/requirements/quality.txt
 commands =
-    isort tests test_utils edx_django_utils manage.py setup.py test_settings.py
+    isort edx_django_utils manage.py setup.py test_settings.py