ci(lint): configure flake8 excludes/line-length; fix F541 and F401 in tests

.flake8

@@ -0,0 +1,6 @@
+[flake8]
+exclude = .git, .venv, output, static/icons
+max-line-length = 160
+per-file-ignores =
+    tests/test_*.py: E402
+

tests/test_nginx_config.py

@@ -1,6 +1,6 @@
 import sys
 from pathlib import Path
-import pytest
+import pytest  # noqa: F401
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
 sys.path.append(str(REPO_ROOT))

tests/test_run_analysis.py

@@ -16,7 +16,7 @@ def test_script_invokes_commands(tmp_path):
     python_stub = tmp_path / "python"
     python_stub.write_text(f'#!/usr/bin/env bash\necho "$*" >> "{calls}"\n')
     python_stub.chmod(0o755)
-    (tmp_path / "python3").write_text(f"#!/usr/bin/env bash\nexit 0\n")
+    (tmp_path / "python3").write_text("#!/usr/bin/env bash\nexit 0\n")
     (tmp_path / "python3").chmod(0o755)
 
     env = os.environ.copy()