As near as I can tell, Py_Initialize() is causing the stdout mode to change from O_TEXT to O_BINARY in _testembed.

Looking at the output in this test, you can see the first printf('\n') (after 'Use defaults') is correctly translated, but the next '\n' comes after Py_Initialize().

b'--- Use defaults ---\r\n... \r\n--- Set encoding only ---\n...'

I don't really see how this can be avoided without breaking something else to do with text IO. Probably the documentation for Py_Initialize should get the note, rather than the What's New section. Py_Initialize has really brief docs, and I'm certain there are plenty of other little things like this that change when you call it - is this the right place for compiler-specific caveats like this? I don't really know where else it could go. Or is it something that we really do want to fix? (We generally avoid changing global settings like this where possible.)