Add flake8 and mypy (type) checking for Python scripts

.flake8

@@ -0,0 +1,4 @@
+[flake8]
+ignore = 
+  # E501 line too long
+  E501,

.github/workflows/ringrtc.yml

@@ -30,11 +30,17 @@ jobs:
         cache-targets: "false"
     - name: Install protoc
       run: sudo apt-get update && sudo apt-get install -y protobuf-compiler
+    - name: Install Python tools
+      run: pip3 install flake8 mypy
     - uses: actions/checkout@v4
     - run: rustup toolchain install $(cat rust-toolchain) --profile minimal --component clippy --target aarch64-linux-android,aarch64-apple-ios
     - name: Install extra Rust tools
       run: cargo +stable install --version 0.5.6 --locked cargo-about
     - run: shellcheck **/*.sh bin/build-aar bin/build-call_sim-cli bin/build-cli bin/build-electron bin/build-gctc bin/build-ios bin/build-javadoc bin/build-rustdoc bin/build-target bin/fetch-artifact bin/gsync-webrtc bin/prepare-workspace bin/rust-lint-check bin/set-up-for-cocoapods src/rust/scripts/run-tests
+    # Skip the Python scripts not written with flake8 style. (Try not to add more.)
+    - run: cd bin && python3 -m flake8 . --exclude build-aar.py,logs-notebook/call_log_parser.py,logs-notebook/emos.py,measure-cpu.py,parse_log.py,print_build_env.py
+    # Only include typed Python scripts here.
+    - run: python3 -m mypy --python-version 3.8 --strict bin/convert_webrtc_acknowledgments.py bin/fetch-artifact.py
     - name: Check acknowledgments
       run: ./bin/regenerate_acknowledgments.sh && git diff --name-status --exit-code acknowledgments
     - name: Clippy

bin/build-webrtc.py

@@ -56,7 +56,7 @@ def verify_build_host_platform(target_platform):
     if target_platform == 'android' or target_platform == 'linux':
         expected_os_major_version = 'Ubuntu 22'
         actual_os = subprocess.check_output(['lsb_release', '--short', '--description']).decode('UTF-8')
-        if not expected_os_major_version in actual_os:
+        if expected_os_major_version not in actual_os:
             raise Exception(f"Invalid Host OS Major Version. Expected: {expected_os_major_version} Actual: {actual_os}")
     elif target_platform == 'ios' or target_platform == 'mac':
         expected_system = 'Darwin'