github: switch the python checker CI to use something that is maintained

The python-lint action was last updated 3 years ago. It contains very
old versions of the lint tools, including pre-1.0 versions of mypy. It
doesn't allow installing dependencies for mypy to robustly typecheck.

Simply installing the tools ourselves and running them directly is
simpler, shorter, easier, and provides better linting analysis. So, do
so.

In the process, we can remove a `# type: ignore` from lddtree.py;
argcomplete has typing info. So does pyelftools, but only in git master.

.github/workflows/python.yml

@@ -10,19 +10,18 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    # NB: v1.4.0 covers Python 3.8.
-    - uses: ricardochaves/python-lint@v1.4.0
+    - uses: actions/setup-python@v5
       with:
-        python-root-list: lddtree.py pylint
-        use-pylint: true
-        use-pycodestyle: false
-        use-flake8: false
-        use-black: true
-        use-mypy: true
-        use-isort: true
-        extra-pylint-options: ""
-        extra-pycodestyle-options: ""
-        extra-flake8-options: ""
-        extra-black-options: ""
-        extra-mypy-options: ""
-        extra-isort-options: ""
+        python-version: '3.x'
+    - name: install dependencies
+      run: |
+        python -m pip install pylint mypy black 'isort[colors]'
+        # mypy dependencies for following imported types
+        python -m pip install argcomplete
+    - run: pylint --output-format colorized lddtree.py
+    - run: mypy lddtree.py
+      env:
+        TERM: xterm-color
+        MYPY_FORCE_COLOR: 1
+    - run: black --check --diff --color lddtree.py
+    - run: isort --check --diff --color lddtree.py

lddtree.py

@@ -56,7 +56,7 @@
 # Disable import errors for all 3rd party modules.
 # pylint: disable=import-error
 try:
-    import argcomplete  # type: ignore
+    import argcomplete
 except ImportError:
     argcomplete = cast(Any, None)