os.stat() raises exception UnicodeEncodeError when path is unicode and no locale is set in envinronment (this occures when running app with daemon tools -> LC_ALL=)

How to simulate:
$ env -i python
>>> import os
>>> os.stat(u"\xf0")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode character u'\xf0' in position 0: ordinal not in range(128)

Is this a valid behaviour? Then maybe some notification in documentation would be nice (I am using os.path.isfile and now UnicodeEncodeError raised...)

Thanks
Ondra