embedding: getting exception information?

Hi,

I'm embedding python in a COM object and want to get the information usually
printed via PyErr_Print. I tried code like this:

dict ns(... dict of __main__ like in the example ...);
try {
    handle<>(PyRun_String("import non_existing_module\n",
    Py_file_input,ns.ptr(),ns.ptr()));
} catch (error_already_set) {
    // try to write error information to StringIO buffer
    PyRun_String("import traceback,sys,StringIO\n"
    "buf = StringIO.StringIO()\n"
    "traceback.print_tb(sys.exc_info()[2],None,buf)\n"
    "error = buf.getvalue()\n",
    Py_file_input,ns.ptr(),ns.ptr());
    PyErr_Clear();
    std::string error = extract<std::string>(ns["error"]);
}

I tried also to use extract<const char*> but in both cases I get an
exception in this line. I first tried to get the error information using the
C API, but I could not find a solution. Af a little bit of googling I found
this solution, but I don't know if it's ok: There is still an active
exception, so could I safely continue to use the interpreter to output the
error?
Has somebody an working example on how to get the traceback or could point
me to the right direction?

regards,
Achim