Issue #1559549: Add 'name' and 'path' attributes to ImportError.

Currently import does not use these attributes as they are planned
for use by importlib (which will be another commit).

Thanks to Filip Gruszczyński for the initial patch and Brian Curtin
for refining it.

Python/errors.c

@@ -585,6 +585,53 @@ PyObject *PyErr_SetFromWindowsErrWithUnicodeFilename(
 }
 #endif /* MS_WINDOWS */
 
+PyObject *
+PyErr_SetExcWithArgsKwargs(PyObject *exc, PyObject *args, PyObject *kwargs)
+{
+    PyObject *val;
+
+    /* args must at least be an empty tuple */
+    if (args == NULL)
+        args = PyTuple_New(0);
+
+    val = PyObject_Call(exc, args, kwargs);
+    if (val != NULL) {
+        PyErr_SetObject((PyObject *) Py_TYPE(val), val);
+        Py_DECREF(val);
+    }
+
+    return NULL;
+}
+
+PyObject *
+PyErr_SetFromImportErrorWithNameAndPath(PyObject *msg,
+                                        PyObject *name, PyObject *path)
+{
+    PyObject *args = PyTuple_New(1);
+    PyObject *kwargs = PyDict_New();
+    PyObject *result;
+
+    if (path == NULL)
+        path = Py_None;
+
+    PyTuple_SetItem(args, 0, msg);
+    PyDict_SetItemString(kwargs, "name", name);
+    PyDict_SetItemString(kwargs, "path", path);
+
+    result = PyErr_SetExcWithArgsKwargs(PyExc_ImportError, args, kwargs);
+
+    Py_DECREF(args);
+    Py_DECREF(kwargs);
+
+    return result;
+}
+
+PyObject *
+PyErr_SetFromImportErrorWithName(PyObject *msg, PyObject *name)
+{
+    return PyErr_SetFromImportErrorWithNameAndPath(msg, name, NULL);
+}
+
 void
 _PyErr_BadInternalCall(const char *filename, int lineno)
 {