Change PyErr_Format() to generate a unicode string (by using
PyUnicode_FromFormatV() instead of PyString_FromFormatV()).

Change calls to PyErr_Format() to benefit from the new format
specifiers: Using %S, object instead of %s, PyString_AS_STRING(object)
with will work with unicode objects too.
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index c72a5bd..1f7b2ca 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -173,8 +173,7 @@
 	PyObject *, Py_UNICODE *);
 #endif /* Py_WIN_WIDE_FILENAMES */
 
-PyAPI_FUNC(PyObject *) PyErr_Format(PyObject *, const char *, ...)
-			Py_GCC_ATTRIBUTE((format(printf, 2, 3)));
+PyAPI_FUNC(PyObject *) PyErr_Format(PyObject *, const char *, ...);
 
 #ifdef MS_WINDOWS
 PyAPI_FUNC(PyObject *) PyErr_SetFromWindowsErrWithFilenameObject(