Exception Chaining missing method for suppressing context

Doc/c-api/exceptions.rst

 .. highlightlang:: c
 
 
 .. _exceptionhandling:
 
 ******************
 Exception Handling
 ******************
 
 The functions described in this chapter will let you handle and raise Python
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 .. c:function:: void PyException_SetContext(PyObject *ex, PyObject *ctx)
 
    Set the context associated with the exception to *ctx*.  Use *NULL* to clear
    it.  There is no type check to make sure that *ctx* is an exception instance.
    This steals a reference to *ctx*.
 
 
 .. c:function:: PyObject* PyException_GetCause(PyObject *ex)
 
-   Return the cause (another exception instance set by ``raise ... from ...``)
-   associated with the exception as a new reference, as accessible from Python
-   through :attr:`__cause__`.  If there is no cause associated, this returns
-   *NULL*.
+   Return the cause (either an exception instance, or :keyword:`None`,
+   set by ``raise ... from ...``) associated with the exception as a new
+   reference, as accessible from Python through :attr:`__cause__`.  
+   
+   If there is no cause associated, this returns *NULL* (from Python
+   ``__cause__ is Ellipsis``).  If the cause is :keyword:`None`, the default
+   exception display routines stop showing the context chain.
 
 
 .. c:function:: void PyException_SetCause(PyObject *ex, PyObject *ctx)
 
    Set the cause associated with the exception to *ctx*.  Use *NULL* to clear
-   it.  There is no type check to make sure that *ctx* is an exception instance.
-   This steals a reference to *ctx*.
+   it.  There is no type check to make sure that *ctx* is either an exception
+   instance or :keyword:`None`.  This steals a reference to *ctx*.
+
+   If the cause is set to :keyword:`None` the default exception display
+   routines will not display this exception's context, and will not follow the
+   chain any further.
 
 
 .. _unicodeexceptions:
 
 Unicode Exception Objects
 =========================
 
 The following functions are used to create and modify Unicode exceptions from C.
 
 .. c:function:: PyObject* PyUnicodeDecodeError_Create(const char *encoding, const char *object, Py_ssize_t length, Py_ssize_t start, Py_ssize_t end, const char *reason)
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 (1)
    This is a base class for other standard exceptions.
 
 (2)
    This is the same as :exc:`weakref.ReferenceError`.
 
 (3)
    Only defined on Windows; protect code that uses this by testing that the
    preprocessor macro ``MS_WINDOWS`` is defined.