Issue #21578: Fixed misleading error message when ImportError called with

invalid keyword args.

Lib/test/test_exceptions.py

@@ -1096,6 +1096,22 @@ class ImportErrorTests(unittest.TestCase):
         self.assertEqual(exc.name, 'somename')
         self.assertEqual(exc.path, 'somepath')
 
+        msg = "'invalid' is an invalid keyword argument for this function"
+        with self.assertRaisesRegex(TypeError, msg):
+            ImportError('test', invalid='keyword')
+
+        with self.assertRaisesRegex(TypeError, msg):
+            ImportError('test', name='name', invalid='keyword')
+
+        with self.assertRaisesRegex(TypeError, msg):
+            ImportError('test', path='path', invalid='keyword')
+
+        with self.assertRaisesRegex(TypeError, msg):
+            ImportError(invalid='keyword')
+
+        with self.assertRaisesRegex(TypeError, msg):
+            ImportError('test', invalid='keyword', another=True)
+
     def test_non_str_argument(self):
         # Issue #15778
         with check_warnings(('', BytesWarning), quiet=True):

Misc/NEWS

@@ -10,6 +10,9 @@ What's New in Python 3.7.0 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #21578: Fixed misleading error message when ImportError called with
+  invalid keyword args.
+
 - Issue #28203: Fix incorrect type in complex(1.0, {2:3}) error message.
   Patch by Soumya Sharma.
 

Objects/exceptions.c

@@ -612,36 +612,38 @@ SimpleExtendsException(PyExc_BaseException, KeyboardInterrupt,
 static int
 ImportError_init(PyImportErrorObject *self, PyObject *args, PyObject *kwds)
 {
+    static char *kwlist[] = {"name", "path", 0};
+    PyObject *empty_tuple;
     PyObject *msg = NULL;
     PyObject *name = NULL;
     PyObject *path = NULL;
 
-/* Macro replacement doesn't allow ## to start the first line of a macro,
+    if (BaseException_init((PyBaseExceptionObject *)self, args, NULL) == -1)
-   so we move the assignment and NULL check into the if-statement. */
-#define GET_KWD(kwd) { \
-    kwd = PyDict_GetItemString(kwds, #kwd); \
-    if (kwd) { \
-        Py_INCREF(kwd); \
-        Py_XSETREF(self->kwd, kwd); \
-        if (PyDict_DelItemString(kwds, #kwd)) \
-            return -1; \
-    } \
-    }
-
-    if (kwds) {
-        GET_KWD(name);
-        GET_KWD(path);
-    }
-
-    if (BaseException_init((PyBaseExceptionObject *)self, args, kwds) == -1)
-        return -1;
-    if (PyTuple_GET_SIZE(args) != 1)
-        return 0;
-    if (!PyArg_UnpackTuple(args, "ImportError", 1, 1, &msg))
         return -1;
 
-    Py_INCREF(msg);
+    empty_tuple = PyTuple_New(0);
-    Py_XSETREF(self->msg, msg);
+    if (!empty_tuple)
+        return -1;
+    if (!PyArg_ParseTupleAndKeywords(empty_tuple, kwds, "|$OO:ImportError", kwlist,
+                                     &name, &path)) {
+        Py_DECREF(empty_tuple);
+        return -1;
+    }
+    Py_DECREF(empty_tuple);
+
+    if (name) {
+        Py_INCREF(name);
+        Py_XSETREF(self->name, name);
+    }
+    if (path) {
+        Py_INCREF(path);
+        Py_XSETREF(self->path, path);
+    }
+    if (PyTuple_GET_SIZE(args) == 1) {
+        msg = PyTuple_GET_ITEM(args, 0);
+        Py_INCREF(msg);
+        Py_XSETREF(self->msg, msg);
+    }
 
     return 0;
 }