It looks like the bug is already fixed in Python trunk:

def uuid4():
    """Generate a random UUID."""

    # When the system provides a version-4 UUID generator, use it.
    if _uuid_generate_random:
        _buffer = ctypes.create_string_buffer(16)
        _uuid_generate_random(_buffer)
        return UUID(bytes=_buffer.raw)
    ...

Changeset: r67318. The changeset was not related to this issue, but 
#4363 (Make uuid module functions usable without ctypes).