Fix: Code quality was not enforced

Problem: The code quality of the source code and the scripts was not verified automatically and could result into bugs or noisy commits from other contributors when fixing them.

Solution:

1. Add the tool `flake8` to the CI tests and adds code quality on the runtime Python code.

2. Enable Python tests on the runtime init as well.

3. Add `shellcheck` to check the quality of shell scripts.

.github/workflows/code-quality.yml

@@ -3,7 +3,7 @@ name: Test code quality
 on: push
 
 jobs:
-  code-quality:
+  code-quality-python:
     runs-on: ubuntu-22.04
 
     steps:
@@ -26,16 +26,37 @@ jobs:
       - name: Test with Black
         run: |
           black --check ./vm_supervisor
+          black --check ./runtimes/aleph-debian-11-python/init1.py
 
       - name: Test with isort
         run: |
           isort --check-only --profile=black ./vm_supervisor
+          isort --check-only --profile=black ./runtimes/aleph-debian-11-python/init1.py
 
       - name: Test with MyPy
         run: |
           mypy --ignore-missing-imports ./vm_supervisor
-#          mypy --config-file ./mypy.ini ./vm_supervisor
+          mypy --ignore-missing-imports ./runtimes/aleph-debian-11-python/init1.py
 
-#      - name: Test with flake8
-#        run: |
-#          flake8 ./vm_supervisor
+      - name: Test with flake8
+        run: |
+          flake8 --extend-ignore E501 ./vm_supervisor
+          flake8 --extend-ignore E501,E402 ./runtimes/aleph-debian-11-python/init1.py
+
+  code-quality-shell:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Workaround github issue https://github.com/actions/runner-images/issues/7192
+        run: sudo echo RESET grub-efi/install_devices | sudo debconf-communicate grub-pc
+
+      - name: Install required system packages only for Ubuntu Linux
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y shellcheck
+
+      - name: Run Shellcheck on all shell scripts
+        run: |
+          find ./ -type f -name "*.sh" -exec shellcheck {} \;