Test fails on non-utf8 locale. $ LC_ALL=en_US ./python -m test.regrtest -v -m test_no_ensure_ascii_flag test_json ... ====================================================================== FAIL: test_no_ensure_ascii_flag (test.test_json.test_tool.TestTool) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/serhiy/py/cpython/Lib/test/test_json/test_tool.py", line 115, in test_no_ensure_ascii_flag self.assertEqual(out.splitlines(), b'"\\u6e2c\\u8a66"\n'.splitlines()) AssertionError: Lists differ: [b'"\\u00e6\\u00b8\\u00ac\\u00e8\\u00a9\\u00a6"'] != [b'"\\u6e2c\\u8a66"'] First differing element 0: b'"\\u00e6\\u00b8\\u00ac\\u00e8\\u00a9\\u00a6"' b'"\\u6e2c\\u8a66"' - [b'"\\u00e6\\u00b8\\u00ac\\u00e8\\u00a9\\u00a6"'] + [b'"\\u6e2c\\u8a66"'] ----------------------------------------------------------------------