On 10.11.2013 14:03, Nick Coghlan wrote: > > Updated patch (v5) with a more robust chaining mechanism provided as a private "_PyErr_TrySetFromCause" API. This version eliminates the previous whitelist in favour of checking directly for the ability to replace the exception with another instance of the same type without losing information. > > This version also has more direct tests of the exception wrapping behaviour as a dedicated test class. > > If I don't hear any objections in the next couple of days, I plan to commit this version. This doesn't look right: diff -r 1ee45eb6aab9 Include/pyerrors.h --- a/Include/pyerrors.h	Sat Nov 09 23:15:52 2013 +0200 +++ b/Include/pyerrors.h	Sun Nov 10 22:54:04 2013 +1000 ... +PyAPI_FUNC(PyObject *) _PyErr_TrySetFromCause( + const char *prefix_format, /* ASCII-encoded string */ + ... + ); BTW: Why don't we make that API a public one ? It could be useful in C extensions as well. In the error messages, I'd use "codecs.encode()" and "codecs.decode()" (ie. with parens) instead of "codecs.encode" and "codecs.decode".