tools: handle container env in generate-test-cases

When we are running inside a container we generally wont be booted
with systemd and thus systemctl will fail. Fall back to check for
the dnf json socket by checking the path exists and bail otherwise.

tools/test-case-generators/generate-test-cases

@@ -63,8 +63,13 @@ class TestCaseGenerator:
     def __init__(self, test_case_request):
         self.test_case = test_case_request
 
-    def get_test_case(self, no_image_info, store):
-        compose_request = json.dumps(self.test_case["compose-request"])
+    def ensure_dnf_json(self):
+        if os.path.exists("/.dockerenv"):
+            if os.path.exists("/run/osbuild-dnf-json/api.sock"):
+                # assume we are good to go
+                return
+            print("running in container and no dnf-json socket found")
+            sys.exit(1)
 
         command = ["systemctl", "is-active", "--quiet", "osbuild-dnf-json.socket"]
         if not is_subprocess_succeeding(command):
@@ -74,6 +79,11 @@ class TestCaseGenerator:
                 print("impossible to start osbuild-dnf-json.socket with systemd")
                 sys.exit(1)
 
+    def get_test_case(self, no_image_info, store):
+        compose_request = json.dumps(self.test_case["compose-request"])
+
+        self.ensure_dnf_json()
+
         pipeline_command = ["go", "run", "./cmd/osbuild-pipeline", "-"]
         self.test_case["manifest"] = json.loads(get_subprocess_stdout(pipeline_command, input=compose_request, encoding="utf-8"))