improved PEP 409 implementation

Include/pyerrors.h

 #ifndef Py_ERRORS_H
 #define Py_ERRORS_H
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /* Error objects */
 
 #ifndef Py_LIMITED_API
 /* PyException_HEAD defines the initial segment of every exception class. */
 #define PyException_HEAD PyObject_HEAD PyObject *dict;\
              PyObject *args; PyObject *traceback;\
-             PyObject *context; PyObject *cause;
+             PyObject *context; PyObject *cause;\
+             int suppress_context;
 
 typedef struct {
     PyException_HEAD
 } PyBaseExceptionObject;
 
 typedef struct {
     PyException_HEAD
     PyObject *msg;
     PyObject *filename;
     PyObject *lineno;
@@ skipping 74 matching lines @@
 PyAPI_FUNC(int) PyErr_ExceptionMatches(PyObject *);
 PyAPI_FUNC(void) PyErr_NormalizeException(PyObject**, PyObject**, PyObject**);
 
 /* Traceback manipulation (PEP 3134) */
 PyAPI_FUNC(int) PyException_SetTraceback(PyObject *, PyObject *);
 PyAPI_FUNC(PyObject *) PyException_GetTraceback(PyObject *);
 
 /* Cause manipulation (PEP 3134) */
 PyAPI_FUNC(PyObject *) PyException_GetCause(PyObject *);
 PyAPI_FUNC(void) PyException_SetCause(PyObject *, PyObject *);
-PyAPI_FUNC(int) _PyException_SetCauseChecked(PyObject *, PyObject *);
 
 /* Context manipulation (PEP 3134) */
 PyAPI_FUNC(PyObject *) PyException_GetContext(PyObject *);
 PyAPI_FUNC(void) PyException_SetContext(PyObject *, PyObject *);
 
 
 /* */
 
 #define PyExceptionClass_Check(x)                                       \
     (PyType_Check((x)) &&                                               \
@@ skipping 287 matching lines @@
 #include <stdarg.h>
 PyAPI_FUNC(int) PyOS_snprintf(char *str, size_t size, const char  *format, ...)
                         Py_GCC_ATTRIBUTE((format(printf, 3, 4)));
 PyAPI_FUNC(int) PyOS_vsnprintf(char *str, size_t size, const char  *format, va_list va)
                         Py_GCC_ATTRIBUTE((format(printf, 3, 0)));
 
 #ifdef __cplusplus
 }
 #endif
 #endif /* !Py_ERRORS_H */