test-case-generators: report errors from child processes

The current implementation does not report any errors because it uses
the subprocess.check_output function from Python std library. The
function is convenient to use but it hides all the errors from us which
makes it very inconvenient when the test generation often fails (like
developing support for alternative architecture). This patch introduces
a wrapper around the subprocess.run function which dumps the
subprocess's stdout to stderr in case of failure and forwards it to the
caller in case of success. This way the generation code is still very
straight forward, but the errors are reported properly.

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

@@ -26,9 +26,18 @@ It then outputs a json test case as standard output.
 '''
 
 
+def get_subprocess_stdout(*args, **kwargs):
+    sp = subprocess.run(*args, **kwargs, stdout=subprocess.PIPE)
+    if sp.returncode != 0:
+        sys.stderr.write(sp.stdout)
+        sys.exit(1)
+    
+    return sp.stdout
+
+
 def run_osbuild(manifest, store):
     osbuild_cmd = ["osbuild", "--store", store, "--json", "-"]
-    result = json.loads(subprocess.check_output(osbuild_cmd, encoding="utf-8", input=json.dumps(manifest)))
+    result = json.loads(get_subprocess_stdout(osbuild_cmd, encoding="utf-8", input=json.dumps(manifest)))
     return result.get("output_id")
 
 
@@ -37,10 +46,10 @@ def main(test_case, store):
     compose_request = json.dumps(test_case["compose-request"])
 
     pipeline_command = ["go", "run", "./cmd/osbuild-pipeline", "-"]
-    test_case["manifest"] = json.loads(subprocess.check_output(pipeline_command, input=compose_request, encoding="utf-8"))
+    test_case["manifest"] = json.loads(get_subprocess_stdout(pipeline_command, input=compose_request, encoding="utf-8"))
 
     pipeline_command = ["go", "run", "./cmd/osbuild-pipeline", "-rpmmd", "-"]
-    test_case["rpmmd"] = json.loads(subprocess.check_output(pipeline_command, input=compose_request, encoding="utf-8"))
+    test_case["rpmmd"] = json.loads(get_subprocess_stdout(pipeline_command, input=compose_request, encoding="utf-8"))
 
     if boot_type != "nspawn-extract":
         output_id = run_osbuild(test_case["manifest"], store)
@@ -53,7 +62,7 @@ def main(test_case, store):
                 with open(fn, "w") as f:
                     subprocess.run(["xz", "--decompress", "--stdout", image_file], stdout=f)
                 image_file = fn
-        test_case["image-info"] = json.loads(subprocess.check_output(["tools/image-info", image_file]))
+        test_case["image-info"] = json.loads(get_subprocess_stdout(["tools/image-info", image_file], encoding="utf-8"))
 
     return test_case
 

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

@@ -6,6 +6,14 @@ import json
 import os
 import sys
 
+def get_subprocess_stdout(*args, **kwargs):
+    sp = subprocess.run(*args, **kwargs, stdout=subprocess.PIPE)
+    if sp.returncode != 0:
+        sys.stderr.write(sp.stdout)
+        sys.exit(1)
+    
+    return sp.stdout
+
 def main(distro, arch, store, output):
     with open("tools/test-case-generators/format-request-map.json") as format_request_json:
         format_request_dict = json.load(format_request_json)
@@ -15,7 +23,7 @@ def main(distro, arch, store, output):
         test_case_request["compose-request"]["distro"] = distro
         test_case_request["compose-request"]["arch"] = arch
         test_case_request["compose-request"]["repositories"] = repos_dict[distro][arch]
-        test_case = json.loads(subprocess.check_output(["tools/test-case-generators/generate-test-case", store], input=json.dumps(test_case_request), encoding="utf-8"))
+        test_case = json.loads(get_subprocess_stdout(["tools/test-case-generators/generate-test-case", store], input=json.dumps(test_case_request), encoding="utf-8"))
         name = distro.replace("-", "_") + "-" + arch + "-" + output_format.replace("-", "_") + "-boot.json"
         file_name = output + "/" + name
         with open(file_name, 'w') as case_file: