Fix CalledProcessError attribute access in tests (#12838)

tests/test_builders/test_build_texinfo.py

@@ -34,7 +34,7 @@ def test_texinfo(app):
     except CalledProcessError as exc:
         print(exc.stdout)
         print(exc.stderr)
-        msg = f'makeinfo exited with return code {exc.retcode}'
+        msg = f'makeinfo exited with return code {exc.returncode}'
         raise AssertionError(msg) from exc