osbuild: add meta module for metadata information

This new module contains utilities that help to introspect parts
that constitute the inner parts of osbuild, i.e. its stages
and assembler (which is also considered a type of stage in
this context). It contains the `StageInfo` class that can that
contains meta-information about the individual stage, such as
a short information (`info`), a longer description (`desc`) and
its JSON schema. A new Schema class represents schema data and
has a `validation` method that can be used to validate that json
data conforms to said schema.
A `Index` class can be used to obtain `StageInfo` and `Schema`
for entities identified via `klass` and `name`.
A top level `validate` method is introduced that can validate
manifest data.
Internally it uses the `jsonschema` package so add that as a
requirement and Install this dependency in the CI.

.github/workflows/runtime-tests.yml

@@ -31,6 +31,8 @@ jobs:
       uses: actions/setup-python@v1
       with:
         python-version: 3.7
+    - name: Install Python Packages
+      run: pip install jsonschema
     - name: "Run Pipeline Tests"
       run: sudo env "PATH=$PATH" make test-runtime
 
@@ -49,6 +51,8 @@ jobs:
       uses: actions/setup-python@v1
       with:
         python-version: 3.7
+    - name: Install Python Packages
+      run: pip install jsonschema
     - name: "Run Noop-Pipeline Tests"
       run: |
         for i in {0..2} ; do
@@ -75,6 +79,8 @@ jobs:
       uses: actions/setup-python@v1
       with:
         python-version: 3.7
+    - name: Install Python Packages
+      run: pip install jsonschema
     - name: "Run Assembler Tests"
       run: sudo env "PATH=$PATH" python3 -m unittest -v test.test_assemblers
 
@@ -95,5 +101,7 @@ jobs:
       uses: actions/setup-python@v1
       with:
         python-version: 3.7
+    - name: Install Python Packages
+      run: pip install jsonschema
     - name: "Run Stage Tests"
       run: sudo env "PATH=$PATH" python3 -m unittest -v test.test_stages

.github/workflows/tests.yml

@@ -9,7 +9,7 @@ jobs:
     container: docker.io/library/python:3.7
     steps:
       - name: Install pylint
-        run: pip install pylint==2.4.1
+        run: pip install pylint==2.4.1 jsonschema
       - name: Clone repository
         uses: actions/checkout@v2
       - name: Run pylint
@@ -67,6 +67,9 @@ jobs:
         with:
           path: osbuild
 
+      - name: Install Dependencies
+        run: pip install jsonschema
+
       - name: Run test_osbuild
         run: |
           cd osbuild