diff -r 6b3be9f38f2a Include/pyerrors.h
--- a/Include/pyerrors.h	Tue Oct 18 13:23:18 2016 +0300
+++ b/Include/pyerrors.h	Tue Oct 18 13:55:07 2016 +0300
@@ -254,6 +254,17 @@ PyAPI_FUNC(PyObject *) PyErr_FormatV(
     va_list vargs);
 #endif
 
+#ifndef Py_LIMITED_API
+/* Like PyErr_Format(), but saves current exception as __context__ and
+   __cause__.
+ */
+PyAPI_FUNC(PyObject *) _PyErr_FormatFromCause(
+    PyObject *exception,
+    const char *format,   /* ASCII-encoded string  */
+    ...
+    );
+#endif
+
 #ifdef MS_WINDOWS
 PyAPI_FUNC(PyObject *) PyErr_SetFromWindowsErrWithFilename(
     int ierr,
diff -r 6b3be9f38f2a Modules/zipimport.c
--- a/Modules/zipimport.c	Tue Oct 18 13:23:18 2016 +0300
+++ b/Modules/zipimport.c	Tue Oct 18 13:55:07 2016 +0300
@@ -907,10 +907,8 @@ read_directory(PyObject *archive)
     fp = _Py_fopen_obj(archive, "rb");
     if (fp == NULL) {
         if (PyErr_ExceptionMatches(PyExc_OSError)) {
-            PyObject *exc, *val, *tb;
-            PyErr_Fetch(&exc, &val, &tb);
-            PyErr_Format(ZipImportError, "can't open Zip file: %R", archive);
-            _PyErr_ChainExceptions(exc, val, tb);
+            _PyErr_FormatFromCause(ZipImportError,
+                                   "can't open Zip file: %R", archive);
         }
         return NULL;
     }
diff -r 6b3be9f38f2a Objects/abstract.c
--- a/Objects/abstract.c	Tue Oct 18 13:23:18 2016 +0300
+++ b/Objects/abstract.c	Tue Oct 18 13:55:07 2016 +0300
@@ -2118,20 +2118,18 @@ PyObject*
     }
     else {
         if (err_occurred) {
-            PyObject *exc, *val, *tb;
-            PyErr_Fetch(&exc, &val, &tb);
-
             Py_DECREF(result);
 
-            if (func)
-                PyErr_Format(PyExc_SystemError,
-                             "%R returned a result with an error set",
-                             func);
-            else
-                PyErr_Format(PyExc_SystemError,
-                             "%s returned a result with an error set",
-                             where);
-            _PyErr_ChainExceptions(exc, val, tb);
+            if (func) {
+                _PyErr_FormatFromCause(PyExc_SystemError,
+                        "%R returned a result with an error set",
+                        func);
+            }
+            else {
+                _PyErr_FormatFromCause(PyExc_SystemError,
+                        "%s returned a result with an error set",
+                        where);
+            }
 #ifdef Py_DEBUG
             /* Ensure that the bug is caught in debug mode */
             Py_FatalError("a function returned a result with an error set");
diff -r 6b3be9f38f2a Objects/genobject.c
--- a/Objects/genobject.c	Tue Oct 18 13:23:18 2016 +0300
+++ b/Objects/genobject.c	Tue Oct 18 13:55:07 2016 +0300
@@ -170,23 +170,10 @@ gen_send_ex(PyGenObject *gen, PyObject *
         if (((PyCodeObject *)gen->gi_code)->co_flags &
               (CO_FUTURE_GENERATOR_STOP | CO_COROUTINE | CO_ITERABLE_COROUTINE))
         {
-            PyObject *exc, *val, *val2, *tb;
             char *msg = "generator raised StopIteration";
             if (PyCoro_CheckExact(gen))
                 msg = "coroutine raised StopIteration";
-            PyErr_Fetch(&exc, &val, &tb);
-            PyErr_NormalizeException(&exc, &val, &tb);
-            if (tb != NULL)
-                PyException_SetTraceback(val, tb);
-            Py_DECREF(exc);
-            Py_XDECREF(tb);
-            PyErr_SetString(PyExc_RuntimeError, msg);
-            PyErr_Fetch(&exc, &val2, &tb);
-            PyErr_NormalizeException(&exc, &val2, &tb);
-            Py_INCREF(val);
-            PyException_SetCause(val2, val);
-            PyException_SetContext(val2, val);
-            PyErr_Restore(exc, val2, tb);
+            _PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
         }
         else {
             PyObject *exc, *val, *tb;
diff -r 6b3be9f38f2a Python/errors.c
--- a/Python/errors.c	Tue Oct 18 13:23:18 2016 +0300
+++ b/Python/errors.c	Tue Oct 18 13:55:07 2016 +0300
@@ -388,6 +388,9 @@ void
         PyObject *exc2, *val2, *tb2;
         PyErr_Fetch(&exc2, &val2, &tb2);
         PyErr_NormalizeException(&exc, &val, &tb);
+        if (tb != NULL) {
+            PyException_SetTraceback(val, tb);
+        }
         Py_DECREF(exc);
         Py_XDECREF(tb);
         PyErr_NormalizeException(&exc2, &val2, &tb2);
@@ -399,6 +402,49 @@ void
     }
 }
 
+static PyObject *
+_PyErr_FormatVFromCause(PyObject *exception, const char *format, va_list vargs)
+{
+    PyObject *exc, *val, *val2, *tb;
+
+    assert(PyErr_Occurred());
+    PyErr_Fetch(&exc, &val, &tb);
+    PyErr_NormalizeException(&exc, &val, &tb);
+    if (tb != NULL) {
+        PyException_SetTraceback(val, tb);
+    }
+
+    Py_DECREF(exc);
+    Py_XDECREF(tb);
+
+    assert(!PyErr_Occurred());
+    PyErr_FormatV(exception, format, vargs);
+    PyErr_Fetch(&exc, &val2, &tb);
+    PyErr_NormalizeException(&exc, &val2, &tb);
+
+    Py_INCREF(val);
+    PyException_SetCause(val2, val);
+    PyException_SetContext(val2, val);
+
+    PyErr_Restore(exc, val2, tb);
+
+    return NULL;
+}
+
+PyObject *
+_PyErr_FormatFromCause(PyObject *exception, const char *format, ...)
+{
+    va_list vargs;
+#ifdef HAVE_STDARG_PROTOTYPES
+    va_start(vargs, format);
+#else
+    va_start(vargs);
+#endif
+    _PyErr_FormatVFromCause(exception, format, vargs);
+    va_end(vargs);
+    return NULL;
+}
+
 /* Convenience functions to set a type error exception and return 0 */
 
 int