test: Log output even if fuzzer failed

test/fuzz/test_runner.py

@@ -106,8 +106,10 @@ def run_once(*, corpus, test_list, build_dir, export_coverage):
             os.path.join(corpus, t),
         ]
         logging.debug('Run {} with args {}'.format(t, args))
-        output = subprocess.run(args, check=True, stderr=subprocess.PIPE, universal_newlines=True).stderr
+        result = subprocess.run(args, stderr=subprocess.PIPE, universal_newlines=True)
+        output = result.stderr
         logging.debug('Output: {}'.format(output))
+        result.check_returncode()
         if not export_coverage:
             continue
         for l in output.splitlines():