PyErr_Warn is decrepated. Use PyErr_WarnEx

Doc/library/warnings.rst

@@ -16,7 +16,7 @@ warrant raising an exception and terminating the program.  For example, one
 might want to issue a warning when a program uses an obsolete module.
 
 Python programmers issue warnings by calling the :func:`warn` function defined
-in this module.  (C programmers use :cfunc:`PyErr_Warn`; see
+in this module.  (C programmers use :cfunc:`PyErr_WarnEx`; see
 :ref:`exceptionhandling` for details).
 
 Warning messages are normally written to ``sys.stderr``, but their disposition