Consider the test case below.

<<<
#!/usr/bin/python
# -*- encoding: utf8 -*-

import curses

def wrapped(screen):
    screen.addstr(0, 0, "ä")
    screen.addstr(0, 1, "ö")
    screen.addstr(0, 2, "ü")
    screen.getch()

if __name__ == "__main__":
    curses.wrapper(wrapped)
>>>

Expected output: "äöü"
Output on py3.3: as expected
Output on py2.7.3: "?ü"
The actual bytes (as determined by strace) were "\303\303\303\274". Observe the inclusion of broken utf8 sequences.

This issue was initially discovered on Debian sid, but independently confirmed on Arch Linux and two more unknown.