bpo-38530: Offer suggestions on AttributeError (#16856)

When printing AttributeError, PyErr_Display will offer suggestions of similar 
attribute names in the object that the exception was raised from:

>>> collections.namedtoplo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'collections' has no attribute 'namedtoplo'. Did you mean: namedtuple?

2 files changed, 8 insertions, 0 deletions

diff --git a/Include/cpython/pyerrors.h b/Include/cpython/pyerrors.h
index 6711e8b..a15082e 100644
--- a/Include/cpython/pyerrors.h
+++ b/Include/cpython/pyerrors.h
@@ -62,6 +62,12 @@ typedef struct {
     PyObject *value;
 } PyStopIterationObject;
 
+typedef struct {
+    PyException_HEAD
+    PyObject *obj;
+    PyObject *name;
+} PyAttributeErrorObject;
+
 /* Compatibility typedefs */
 typedef PyOSErrorObject PyEnvironmentErrorObject;
 #ifdef MS_WINDOWS
diff --git a/Include/internal/pycore_pyerrors.h b/Include/internal/pycore_pyerrors.h
index 9dd66ae..d1af8e9 100644
--- a/Include/internal/pycore_pyerrors.h
+++ b/Include/internal/pycore_pyerrors.h
@@ -86,6 +86,8 @@ PyAPI_FUNC(int) _PyErr_CheckSignalsTstate(PyThreadState *tstate);
 
 PyAPI_FUNC(void) _Py_DumpExtensionModules(int fd, PyInterpreterState *interp);
 
+extern PyObject* _Py_Offer_Suggestions(PyObject* exception);
+
 #ifdef __cplusplus
 }
 #endif