AttributeError: 'NoneType' object has no attribute 'get'

[Alffernandez]

Version
Server version: 4.6.4
Pulp Ansible Version: 0.15.0

Describe the bug
If there are collections published without meta/runtime.yml in the Automation Hub, the upgrade from Automation Hub 4.2 (AAP 1.2) to Automation Hub 4.6 (AAP 2.3) fails with the following error:

TASK [pulp.pulp_installer.pulp_database_config : Run database migrations] ******
fatal: [aap01dhub1new.launcher.int.abnamro.com]: FAILED! => {"changed": true, "cmd": ["/usr/bin/pulpcore-manager", "migrate", "--no-input"],
......
......
  File \"/usr/lib/python3.9/site-packages/pulp_ansible/app/migrations/0030_collectionversion_requires_ansible.py\", line 33, in set_requires_ansible_and_manifest_and_files_json", "    collection_version.requires_ansible = runtime_yaml.get(\"requires_ansible\")", "AttributeError: 'NoneType' object has no attribute 'get'"], 

To Reproduce

1. Install Automation Hub 4.2 (Ansible Automation Platform 1.2.7 Setup Bundle)
2. Publish a collection/s without meta/runtime.yml.
3. Upgrade to Automation Hub 4.6 (Ansible Automation Platform 2.3 Setup Bundle)

Expected behavior
The installer should show a Warning and skip that task if there is a collection without runtime.yml

Additional context
After applying the patch provided by Matthias Dellweg, the upgrade finishes successfully.

           if runtime_metadata:
                try:
                    runtime_yaml = yaml.safe_load(runtime_metadata)
                except YAMLError:
                    log.warning(
                        "CollectionVersion: '{namespace}.{name}-{version}' - 'meta/runtime.yml' is invalid yaml.".format(
                            namespace=collection_version.namespace, name=collection_version.name, version=collection_version.version
                        )
                    )
                else:
                    try:
                        collection_version.requires_ansible = runtime_yaml.get("requires_ansible")
                    except AttributeError:
                        log.warning(
                            "CollectionVersion: '{namespace}.{name}-{version}' - 'meta/runtime.yml' is missing key 'requires_ansible'.".format(
                                namespace=collection_version.namespace, name=collection_version.name, version=collection_version.version
                            )
                        )

            manifest = get_file_obj_from_tarball(tar, "MANIFEST.json", artifact.file.name, raise_exc=False)
            if manifest:
                try:
                    collection_version.manifest = json.load(manifest)
                except JSONDecodeError:
                    log.warning(
                        "CollectionVersion: '{namespace}.{name}-{version}' - 'MANIFEST.json' is invalid json.".format(
                            namespace=collection_version.namespace, name=collection_version.name, version=collection_version.version
                        )
                    )

            files = get_file_obj_from_tarball(tar, "FILES.json", artifact.file.name, raise_exc=False)
            if files:
                try:
                    collection_version.files = json.load(files)
                except JSONDecodeError:
                    log.warning(
                        "CollectionVersion: '{namespace}.{name}-{version}' - 'FILES.json' is invalid json.".format(
                            namespace=collection_version.namespace, name=collection_version.name, version=collection_version.version
                        )
                    )
            collection_version.save()