diff -r 57550e1f57d9 Python/errors.c
--- a/Python/errors.c	Tue Mar 24 14:01:32 2015 +0100
+++ b/Python/errors.c	Tue Mar 24 15:39:47 2015 +0100
@@ -59,6 +59,8 @@ PyErr_SetObject(PyObject *exception, PyO
     PyObject *exc_value;
     PyObject *tb = NULL;
 
+    assert(!PyErr_Occurred());
+
     if (exception != NULL &&
         !PyExceptionClass_Check(exception)) {
         PyErr_Format(PyExc_SystemError,
@@ -75,10 +77,6 @@ PyErr_SetObject(PyObject *exception, PyO
             /* We must normalize the value right now */
             PyObject *args, *fixed_value;
 
-            /* Issue #23571: PyEval_CallObject() must not be called with an
-               exception set */
-            PyErr_Clear();
-
             if (value == NULL || value == Py_None)
                 args = PyTuple_New(0);
             else if (PyTuple_Check(value)) {
@@ -210,6 +208,7 @@ PyErr_GivenExceptionMatches(PyObject *er
 int
 PyErr_ExceptionMatches(PyObject *exc)
 {
+    assert(PyErr_Occurred());
     return PyErr_GivenExceptionMatches(PyErr_Occurred(), exc);
 }
 
@@ -778,9 +777,7 @@ PyErr_FormatV(PyObject *exception, const
 {
     PyObject* string;
 
-    /* Issue #23571: PyUnicode_FromFormatV() must not be called with an
-       exception set, it calls arbitrary Python code like PyObject_Repr() */
-    PyErr_Clear();
+    assert(!PyErr_Occurred());
 
     string = PyUnicode_FromFormatV(format, vargs);