C:\Documents and Settings\Perry>python -U
Traceback (most recent call last):
  File "C:\Python27\lib\site.py", line 548, in <module>
    main()
  File "C:\Python27\lib\site.py", line 537, in main
    aliasmbcs()
  File "C:\Python27\lib\site.py", line 465, in aliasmbcs
    import locale, codecs
  File "C:\Python27\lib\locale.py", line 182, in <module>
    _percent_re = re.compile(r'%(?:\((?P<key>.*?)\))?'
  File "C:\Python27\lib\re.py", line 194, in compile
    return _compile(pattern, flags)
  File "C:\Python27\lib\re.py", line 249, in _compile
    p = sre_compile.compile(pattern, flags)
  File "C:\Python27\lib\sre_compile.py", line 576, in compile
    code = _code(p, flags)
  File "C:\Python27\lib\sre_compile.py", line 561, in _code
    _compile(code, p.data, flags)
  File "C:\Python27\lib\sre_compile.py", line 151, in _compile
    _compile(code, av[1], flags)
  File "C:\Python27\lib\sre_compile.py", line 132, in _compile
    _compile(code, av[2], flags)
  File "C:\Python27\lib\sre_compile.py", line 107, in _compile
    _compile_charset(av, flags, code, fixup, fixes)
  File "C:\Python27\lib\sre_compile.py", line 232, in _compile_charset
    flags & SRE_FLAG_UNICODE):
  File "C:\Python27\lib\sre_compile.py", line 316, in _optimize_charset
    p = charmap.find(b'\1', q)
TypeError: Type unicode doesn't support the buffer API

Interesting, I didn't even know (remember?) about the -U flag, and it isn't documented.  I guess we don't test it, and I suppose that it is effectively deprecated.  (So others who don't remember don't need to repeat my research: it turns all string literals into unicode literals, which function was added as an experimental tool by Marc Andre in 2000.  I believe it was later superseded by 'from __future__ import unicode_literals', but I didn't research that part.)

This works fine on linux, and the traceback looks like it involves some windows-specific code. 

I'm not sure if this is worth bothering to fix.

So, you write a string literal without a 'u' (or 'b') prefix, and there's no 'from __future__ import unicode_literals' in the module, so you expect it to be a bytestring, but it's not, it's a Unicode string.

I'm not surprised that something breaks!

Well, in this case *he* didn't write the string, it is embedded somewhere in the stdlib.  'python -U' gets you to the python prompt on unix, but apparently not on windows.

But this isn't a feature we support any more, so I'm closing this as won't fix.

What is worse, you write a string literal with a 'b' prefix, and you get a Unicode string.

>>> b''
u''

I tried to use Python with -U (it could be good way to test compatibility with Python 3), but it is totally broken, and there is no hope to fix it.

Reminder: use Python 3 to get an excellent Unicode support everywhere.

> Interesting, I didn't even know (remember?) about the -U flag, and it isn't documented.
https://docs.python.org/2/using/cmdline.html#cmdoption-U

It isn't clear when this broken or why, but I think existing documentation could be adjusted to have a bigger warning around this option.