In short, I do not understand how this passes on Linux. This is python3-3.4.6 on sles12: >>> 'h\xe9\u20ac'.encode('utf-8') b'h\xc3\xa9\xe2\x82\xac' >>> ascii('h\xe9\u20ac'.encode('utf-8')) "b'h\\xc3\\xa9\\xe2\\x82\\xac'" >>> 'h\xe9\u20ac'.encode('utf-8').decode('us-ascii', 'surrogateescape') 'h\udcc3\udca9\udce2\udc82\udcac' >>> This is python3-3.7.0 on AIX: >>> 'h\xe9\u20ac'.encode('utf-8') b'h\xc3\xa9\xe2\x82\xac' >>> ascii('h\xe9\u20ac'.encode('utf-8')) "b'h\\xc3\\xa9\\xe2\\x82\\xac'" >>> 'h\xe9\u20ac'.encode('utf-8').decode('us-ascii', 'surrogateescape') 'h\udcc3\udca9\udce2\udc82\udcac' If I am missing something essential here - please be blunt!