Run ruff in ci.

Fixes #157

Author: jelmer

.github/workflows/test.yml

@@ -33,10 +33,14 @@ jobs:
       - name: Install dependencies
         run: |
           python3 -m pip install --upgrade pip
-          python3 -m pip install --upgrade setuptools wheel setuptools_scm
+          python3 -m pip install --upgrade setuptools wheel setuptools_scm ruff
           python3 -m pip install sphinx
           python3 -m pip install ".[test,twisted]"
 
+      - name: Ruff
+        run: |
+          python -m ruff check .
+
       - name: Tests
         run: |
           python -W once -m testtools.run testtools.tests.test_suite