test: support skip running linters via env variable

Support skip running the linters by setting the environment variable
`SKIP_LINTERS=1`. This flag is useful for distributions.

.github/workflows/ci.yaml

@@ -83,6 +83,40 @@ jobs:
           files: ./coverage.xml
           token: ${{ secrets.CODECOV_TOKEN }}
 
+  skip-linters:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        container:
+          - debian:bookworm-slim
+          - debian:testing-slim
+          - debian:unstable-slim
+          - ubuntu:jammy
+          - ubuntu:noble
+          - ubuntu:oracular
+    container:
+      image: ${{ matrix.container }}
+    steps:
+      - name: Install dependencies
+        run: >
+          apt-get update &&
+          apt-get install --no-install-recommends --yes ca-certificates git
+          pylint python3 python3-coverage python3-ruamel.yaml
+      - uses: actions/checkout@v4
+      - name: Run unit tests
+        run: |
+          SKIP_LINTERS=1 python3 -m coverage run -m unittest discover -v
+          python3 -m coverage xml
+      - name: Install dependencies for Codecov
+        run: apt-get install --no-install-recommends --yes curl gpg gpg-agent
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          fail_ci_if_error: true
+          files: ./coverage.xml
+          token: ${{ secrets.CODECOV_TOKEN }}
+
   system-testing:
     runs-on: ubuntu-latest
     strategy:

tests/test_black.py

@@ -14,6 +14,7 @@
 
 """Run black code formatter in check mode."""
 
+import os
 import subprocess
 import sys
 import unittest
@@ -28,6 +29,7 @@ class BlackTestCase(unittest.TestCase):
     source files is provided by the get_source_files() function.
     """
 
+    @unittest.skipIf(os.environ.get("SKIP_LINTERS"), "requested via SKIP_LINTERS env variable")
     def test_black(self):
         """Test: Run black code formatter on Python source code."""
 

tests/test_flake8.py

@@ -14,6 +14,7 @@
 
 """Run flake8 check."""
 
+import os
 import subprocess
 import sys
 import unittest
@@ -29,6 +30,7 @@ class Flake8TestCase(unittest.TestCase):
     get_source_files() function.
     """
 
+    @unittest.skipIf(os.environ.get("SKIP_LINTERS"), "requested via SKIP_LINTERS env variable")
     def test_flake8(self):
         """Test: Run flake8 on Python source code."""
         cmd = [sys.executable, "-m", "flake8", "--max-line-length=99"] + get_source_files()

tests/test_isort.py

@@ -14,6 +14,7 @@
 
 """Run isort to check if Python import definitions are sorted."""
 
+import os
 import subprocess
 import sys
 import unittest
@@ -28,6 +29,7 @@ class IsortTestCase(unittest.TestCase):
     is provided by the get_source_files() function.
     """
 
+    @unittest.skipIf(os.environ.get("SKIP_LINTERS"), "requested via SKIP_LINTERS env variable")
     def test_isort(self):
         """Test: Run isort on Python source code."""
 

tests/test_pylint.py

@@ -38,6 +38,8 @@ def test_pylint(self):
         """Test: Run pylint on Python source code."""
 
         cmd = [sys.executable, "-m", "pylint", "--rcfile=" + CONFIG, "--"] + get_source_files()
+        if os.environ.get("SKIP_LINTERS"):
+            cmd.insert(4, "--errors-only")
         if unittest_verbosity() >= 2:
             sys.stderr.write(f"Running following command:\n{' '.join(cmd)}\n")
         with subprocess.Popen(

tests/test_shellcheck.py

@@ -14,6 +14,7 @@
 
 """Run shellcheck on Shell code."""
 
+import os
 import subprocess
 import sys
 import unittest
@@ -29,6 +30,7 @@ class ShellcheckTestCase(unittest.TestCase):
     on Shell source code.
     """
 
+    @unittest.skipIf(os.environ.get("SKIP_LINTERS"), "requested via SKIP_LINTERS env variable")
     def test_shellcheck(self):
         """Test: Run shellcheck on Shell source code."""
         cmd = ["shellcheck"] + [get_path(s) for s in SHELL_SCRIPTS]