[Ronald Oussoren, hijacking the "test_struct failure on 64 bit platforms" thread]

The really annoying part of the new struct warnings is that the warning line mentions a line in struct.py instead the caller of struct.pack. That makes it hard to find the source of the warning without telling the warnings module to raise an exception for DeprecationWarnings.

The problem seems to be that Python's C API apparently gives no simple way to supply a value for warning.warn's optional `stacklevel` argument. The C-level signature is: int PyErr_Warn(PyObject *category, char *message); and that's what _struct.c calls. I think it would be good to add a new int PyErr_WarnEx(PyObject *category, char *message, long stacklevel); C API function, change PyErr_Warn to call that forcing stacklevel to 1, and change _struct.c to call PyErr_WarnEx with stacklevel=2. Then it would point at struct.pack()'s caller.