print to stderr

[memsharded]

Changelog: Fix: Make all recipe and plugins python file print() to stderr, so json outputs to stdout are not broken.
Docs: omit

Close #15671

[jcar87]

I like this - but makes me wonder if there are any risks since print is a built-in? thinking of unusual scenarios like a frozen interpreter embedded in an executable - but it looks good otherwise!

[memsharded]

I had a look, and in theory it seems ok, this kind of overwrite of module globals seems allowed, it is not changing the built-in print, just making the module print() pointing to another function, and this is done per-module, not globally.

[AbrilRBS]

Should this be using builtins.print internally? https://docs.python.org/3/library/builtins.html say that's what the builtins map to, but this also seems to work

[memsharded]

Should this be using builtins.print internally? https://docs.python.org/3/library/builtins.html say that's what the builtins map to, but this also seems to work

If we were forced to use the print() name in our replacement, this would be necessary, but as we have control over the loaded module, our own new_print is good too.

[uilianries]

Jenkins will be pleased by this change.