Crash when printing non-unicode

[BenWiederhake]

I hope this is the actual cause of bpython#747. window.py:43 currently says:

self.out_stream.write(msg)

However, this fails when the arument is not encodable in the current encoding.

Here's how to reproduce this is in an Unicode environment:

python3 -c 'import sys; sys.stdout.write("\ud800")'

Fails immediately with:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
UnicodeEncodeError: 'utf-8' codec can't encode character '\ud800' in position 0: surrogates not allowed

So the obvious™ thing to do is call msg.encode(errors='replace') or something.

However:

• What is the charset? Is it still always unicode?
• Is msg really always text?

Those are questions I cannot answer by myself.