while working on a library for raising exceptions in
the context
of another thread, i've come across a bug in
PyThreadState_SetAsyncExc.
if i raise an instance, sys.exc_info() confuses the
exception value for
the exception type, and the exception value is set
None. if i raise the 
type itself, the interpreter creates an instance
internally, but then i can't 
pass arguments to the exception.

see this post for more info
http://mail.python.org/pipermail/python-dev/2006-August/068158.html

Is this still valid? I recall some discussions about raising exceptions
in another thread and don't think the use case is supported.

Agreed.