1 files changed, 22 insertions, 3 deletions
diff --git a/Python/errors.c b/Python/errors.c
index 1f955b5..89021aa 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -619,12 +619,25 @@ PyObject *PyErr_SetFromWindowsErrWithUnicodeFilename(
 #endif /* MS_WINDOWS */
 
 PyObject *
-PyErr_SetImportError(PyObject *msg, PyObject *name, PyObject *path)
+PyErr_SetImportErrorSubclass(PyObject *exception, PyObject *msg,
+    PyObject *name, PyObject *path)
 {
+    int issubclass;
     PyObject *args, *kwargs, *error;
 
-    if (msg == NULL)
+    issubclass = PyObject_IsSubclass(exception, PyExc_ImportError);
+    if (issubclass < 0) {
+        return NULL;
+    }
+    else if (!issubclass) {
+        PyErr_SetString(PyExc_TypeError, "expected a subclass of ImportError");
+        return NULL;
+    }
+
+    if (msg == NULL) {
+        PyErr_SetString(PyExc_TypeError, "expected a message argument");
         return NULL;
+    }
 
     args = PyTuple_New(1);
     if (args == NULL)
@@ -649,7 +662,7 @@ PyErr_SetImportError(PyObject *msg, PyObject *name, PyObject *path)
     PyDict_SetItemString(kwargs, "name", name);
     PyDict_SetItemString(kwargs, "path", path);
 
-    error = PyObject_Call(PyExc_ImportError, args, kwargs);
+    error = PyObject_Call(exception, args, kwargs);
     if (error != NULL) {
         PyErr_SetObject((PyObject *)Py_TYPE(error), error);
         Py_DECREF(error);
@@ -661,6 +674,12 @@ PyErr_SetImportError(PyObject *msg, PyObject *name, PyObject *path)
     return NULL;
 }
 
+PyObject *
+PyErr_SetImportError(PyObject *msg, PyObject *name, PyObject *path)
+{
+    return PyErr_SetImportErrorSubclass(PyExc_ImportError, msg, name, path);
+}
+
 void
 _PyErr_BadInternalCall(const char *filename, int lineno)
 {