This issue is opposed to the PEP 3128:

<< Default error-handler of sys.stdout should be 'backslashreplace'.

Stuff written to stdout might be consumed by another program that might misinterpret the escapes. For interactive session, it is possible to make 'backslashreplace' error-handler to default, but may add confusion of the kind "it works in interactive mode but not when redirecting to a file". >>

But if you read #1602, #5110 and #9198, you will see that not everybody agrees with the PEP.