Fix CI linting workflow (#308)

* ci: No longer fail silently when the expected Python interpreter is missing.

 The tox "lint" target expects Python 3.10 to be installed, but CI only installs Python 3.9. skip_missing_interpreters caused the "lint" workflow in CI to exit successfully, even though no linting was performed.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

* ci: Install Python 3.10 for the "lint" workflow, as expected by the tox configuration.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

* ci: Do not inlcude tox's "lint" environment in the set of "3.9" environments of a GitHub actions run.

Linting is performed explicitly in a separate workflow and does not need to be run as part of the Python 3.9 tests. Additionally, linting currently expects Python 3.10 and will fail during the Python 3.9 test run.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

* build: Dependencies for tox's "lint" environent are installed correctly.

The lint environment requires mypy from the test dependencies to be installed. Although the environment defines `extras = testing`, it also specifies `skip_install = true`, which also skips installation of test dependencies.

This change removes skip_install = true, so that mypy is installed correctly.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

* build: Removed the explicit interpreter version dependency from tox's "version-info" environment.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

.github/workflows/main.yml

@@ -22,7 +22,7 @@ jobs:
         fetch-depth: 0
     - uses: actions/setup-python@v3
       with:
-        python-version: '3.9'
+        python-version: '3.10'
     - name: Install GitHub matcher for ActionLint checker
       run: |
         echo "::add-matcher::.github/actionlint-matcher.json"

tox.ini

@@ -1,7 +1,6 @@
 [tox]
 minversion = 3.14.0
 envlist = py37, py38, py39, py310, lint, version-info, pytest-min
-skip_missing_interpreters = true
 isolated_build = true
 passenv =
     CI
@@ -23,7 +22,6 @@ allowlist_externals =
     make
 
 [testenv:lint]
-skip_install = true
 basepython = python3.10
 extras = testing
 deps =
@@ -41,7 +39,6 @@ commands =
     coverage report
 
 [testenv:version-info]
-basepython = python3.9
 deps =
     packaging == 21.3
 commands =
@@ -51,6 +48,6 @@ commands =
 python =
     3.7: py37, pytest-min
     3.8: py38
-    3.9: py39, lint
+    3.9: py39
     3.10: py310
     pypy3: pypy3