This allows having a meaningful error message when extractUnoException
is called from pyuno_loader::getLoaderModule() (via
raiseRuntimeExceptionWhenNeeded()). If it is called to treat an error
that cropped up in loading uno.py, the old code would abort the whole
operation by throwing an exception because... it gets essentially the
same error. The new code leads to a sensible message on the Python
debug console.